ceph: delete unreachable code in ceph_check_caps()

"revoking & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)" has already
been tested before calling try_nonblocking_invalidate()

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