Revert "ceph: unlock dangling spinlock in try_flush_caps()"

This reverts commit 55d4aa12 which is
commit 6c2838fbdedb9b72a81c931d49e56b229b6cdbca upstream.

The locking issue was not a problem in 3.18, and now sparse rightly
complains about this being an issue, so go back to the "correct" code.

Cc: Jeff Layton <jlayton@redhat.com>
Cc: "Yan, Zheng" <zyan@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>