ceph: re-request max_size if cap auth changes

If the auth cap migrates to another MDS, clear requested_max_size so that
we resend any pending max_size increase requests.  This fixes potential
hangs on writes that extend a file and race with an cap migration between
MDSs.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --cc fs/ceph/caps.c
Simple merge