ceph: reinitialize mds feature bit even when session in open

ceph: reinitialize mds feature bit even when session in open

Following along the same lines as per the user-space fix. Right
now this isn't really an issue with the ceph kernel driver because
of the feature bit laginess, however, that can change over time
(when the new snaprealm info type is ported to the kernel driver)
and depending on the MDS version that's being upgraded can cause
message decoding issues - so, fix that early on.

Link: http://tracker.ceph.com/issues/63188
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>