packet: Always mount node local storage on /mnt/

The rkt pod is exposed with /mnt/ volume[1] and in this PR:

	https://github.com/kinvolk/lokomotive-kubernetes/pull/48/files#diff-b6c7caf796cd86bdcdd936319b1793a1R152

the location where the RAID 0 array is mounted was changed from `/mnt`
to `/mnt/<some-dir>`. This breaks using local volumes in pods, as it
seems the mount is not visible for the rkt container or the kubelet
running in rkt.

This patch just makes the mount location back to `/mnt` for all the cases
(setup_raid, setup_raid_hdd) so it works on all cases, and as those
options are exclusive (only one can be set) this causes no problem at
all.

Other options were considered, like changing the path that is exposed to
rkt container to be /mnt/node-local-storage or
/mnt/node-hdd-local-storage, according to what option was used
(setup_raid, setup_raid_hdd), but that was messy without any good
reason. So, we decided for this, more simpler, approach.

The investigation of the root cause of this issue, to understand why
mounts inside mnt (like in `/mnt/node-local-storage`) are can't be used
by pods and what needs to be changed for that is left as a future patch
(an issue will be created).

This patch is just a minimal fix, a revert, to make this work again on
master.

[1]: https://github.com/kinvolk/lokomotive-kubernetes/blob/d59d071a451f45ac61c2524b94a146a6cde60401/packet/flatcar-linux/kubernetes/workers/cl/worker.yaml.tmpl#L65-L66

packet/flatcar-linux/kubernetes/workers/cl/worker.yaml.tmpl

@@ -195,10 +195,9 @@ storage:
 
             if [ "$${setup_fs_on_raid}" = true ]; then
               mkfs.ext4 "$${device_path}"
-              mkdir "/mnt/$${array_name}"
-              mount "$${device_path}" "/mnt/$${array_name}"
+              mount "$${device_path}" "/mnt/"
               # Make mount persistent across reboots
-              echo "$${device_path} /mnt/$${array_name} ext4 defaults,nofail,discard 0 0" | tee -a /etc/fstab
+              echo "$${device_path} /mnt/ ext4 defaults,nofail,discard 0 0" | tee -a /etc/fstab
             fi
           }
 
@@ -211,17 +210,20 @@ storage:
           # https://www.kernel.org/doc/Documentation/admin-guide/devices.txt
           major_numbers="8,259"
 
+          # XXX: These options are exclusive, as only one fs can be mounted
+          # to /mnt/
+          # This is, partly, because when creating dirs inside /mnt to mount
+          # several paths (like /mnt/node-local-storage), those are not visible
+          # to the pods. See this issue for more info:
+          # https://github.com/kinvolk/lokomotive-kubernetes/issues/73
+          #
           # Variables replaced by Terraform
           if [ ${setup_raid} = true ]; then
             create_data_raid "$${major_numbers}" -1 /dev/md/node-local-storage true
-          else
-             # Both can be set independently
-             if [ ${setup_raid_hdd} = true ]; then
-               create_data_raid "$${major_numbers}" 1 /dev/md/node-local-hdd-storage true
-             fi
-             if [ ${setup_raid_ssd} = true ]; then
-               create_data_raid "$${major_numbers}" 0 /dev/md/node-local-ssd-storage ${setup_raid_ssd_fs}
-             fi
+          elif [ ${setup_raid_hdd} = true ]; then
+            create_data_raid "$${major_numbers}" 1 /dev/md/node-local-hdd-storage true
+          elif [ ${setup_raid_ssd} = true ]; then
+            create_data_raid "$${major_numbers}" 0 /dev/md/node-local-ssd-storage ${setup_raid_ssd_fs}
           fi
     - path: /etc/kubernetes/kubeconfig
       filesystem: root

packet/flatcar-linux/kubernetes/workers/variables.tf

@@ -80,19 +80,19 @@ EOD
 }
 
 variable "setup_raid" {
-  description = "Attempt to create a RAID 0 from extra disks to be used for persistent container storage. Valid values: \"true\", \"false\""
+  description = "Attempt to create a RAID 0 from extra disks to be used for persistent container storage. Can't be used with setup_raid_hdd nor setup_raid_sdd. Valid values: \"true\", \"false\""
   type        = "string"
   default     = "false"
 }
 
 variable "setup_raid_hdd" {
-  description = "Attempt to create a RAID 0 from extra Hard Disk drives only, to be used for persistent container storage. Valid values: \"true\", \"false\""
+  description = "Attempt to create a RAID 0 from extra Hard Disk drives only, to be used for persistent container storage. Can't be used with setup_raid nor setup_raid_sdd. Valid values: \"true\", \"false\""
   type        = "string"
   default     = "false"
 }
 
 variable "setup_raid_ssd" {
-  description = "Attempt to create a RAID 0 from extra Solid State Drives only, to be used for persistent container storage. Valid values: \"true\", \"false\""
+  description = "Attempt to create a RAID 0 from extra Solid State Drives only, to be used for persistent container storage.  Can't be used with setup_raid nor setup_raid_hdd. Valid values: \"true\", \"false\""
   type        = "string"
   default     = "false"
 }