provide ability to adjust deployment strategy

[leelavg]

default value is choosen in such a way to make kubernetes replace one replica when there are 2 replicas running on 2 distinct nodes.

since these replicas are already using leader election a loss of 1 replica during rollout doesn't pose any issues.

minor: fixed a typo s/defautUpdateStrategy/defaultUpdateStrategy/

fixes: #140

[leelavg]

Functionality was already tested as part of linked issue, the defaults and change is checked as below

// new defaults
> k get deploy rbd.csi.ceph.com-ctrlplugin -oyaml | yq -r .spec.strategy
rollingUpdate:
  maxSurge: 0
  maxUnavailable: 1
type: RollingUpdate

// no regression in typo change
> k get ds rbd.csi.ceph.com-nodeplugin -oyaml | yq -r .spec.updateStrategy
rollingUpdate:
  maxSurge: 0
  maxUnavailable: 1
type: RollingUpdate

// when driver spec is updated same is realized in the deployment
> k get deploy rbd.csi.ceph.com-ctrlplugin -oyaml | yq -r .spec.strategy
rollingUpdate:
  maxSurge: 25%
  maxUnavailable: 25%
type: RollingUpdate

[nb-ohad]

@leelavg Can you please reorganize the commit so the first commit holds the API changes (plus generated changes) then a 2nd commit for the changes that are needed to support the new API field in the controller?