ceph: move encode_fh to new API

Use parent_inode has a flag for whether nfsd wants a connectable fh, but
generate one opportunistically so that we can take advantage of the
additional info in there.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>