ceph: remove duplicated filelock ref increase

Inode i_filelock_ref is increased in ceph_lock or ceph_flock, but it is
increased again in ceph_lock_message. This results in this ref won't
become zero. If CEPH_I_ERROR_FILELOCK flag is set in
remove_session_caps once, this flag can't be cleared even if client is
back to normal. So further file lock will return EIO.

Signed-off-by: Zhi Zhang <zhang.david2011@gmail.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>