NFS: Ignore connections that have cl_rpcclient uninitialized
cl_rpcclient starts as ERR_PTR(-EINVAL), and connections like that
are floating freely through the system. Most places check whether
pointer is valid before dereferencing it, but newly added code
in nfs_match_client does not.
Which causes crashes when more than one NFS mount point is present.
Signed-off-by: Petr Vandrovec <petr@vandrovec.name> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>