ceph: fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a couple
of warnings by explicitly adding a break and a goto statements instead
of just letting the code fall through to the next case.

URL: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>