NFS v4.1, v4.2 support

[ghost]

Does sm support NFS v4.2?

If we look in https://github.com/xapi-project/sm/blob/master/drivers/nfs.py
There is a variable here saying 4.1:

    'nfsversion', 'for type=nfs, NFS protocol version - 3, 4, 4.1']

But get_supported_nfs_versions() only look for major, not minor versions. Does it mean it is missing to check if 4.1 is actually supported, or does it mean 4.2 should be supported too?

    """Return list of supported nfs versions."""  
    valid_versions = set(['3', '4'])  
    cv = set()  
    try:  
        ns = util.pread2([RPCINFO_BIN, "-p", "%s" % server])

Looking atrpcinfo -p it can only return major versions of NFS.

# cat /proc/fs/nfsd/versions
-2 -3 +4 +4.1 +4.2
# rpcinfo  -p localhost
   program vers proto   port  service
    100000    4   tcp    111  portmapper
    100000    3   tcp    111  portmapper
    100000    2   tcp    111  portmapper
    100000    4   udp    111  portmapper
    100000    3   udp    111  portmapper
    100000    2   udp    111  portmapper
    100024    1   udp  51368  status
    100024    1   tcp  36643  status
    100005    1   udp  34211  mountd
    100005    1   tcp  47985  mountd
    100005    2   udp  60375  mountd
    100005    2   tcp  50167  mountd
    100005    3   udp  50762  mountd
    100005    3   tcp  33111  mountd
    100003    4   tcp   2049  nfs

A reference issue is #30