client: behave if we can't getattr parents of mount point

client: behave if we can't getattr parents of mount point

If our cap locks us into a subdirectory (e.g., /foo), we will fail to
getattr on its parents (e.g., /).  This is expected.  Tolerate this case,
and warn that quotas may misbehave in that case (if they are set on one of
those parents).

Signed-off-by: Sage Weil <sage@redhat.com>