misc: move daemon stopping function to a generic place

This will be useful for other daemons, like radosgw, in the future.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
rgw: add to ctx.daemons so it can be stopped/started dynamically

Name the daemon after the client it runs on, since only
one per host is supported anyway.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
ceph: allow restarting radosgw

Only split once, since radosgw will have client.X after it.
Monitors and MDSs may have names with more .s as well.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
rgw tests: clean up immediately after the test

There's no need for an explicit cleanup function, so move it back
to where it came from (except in s3roundtrip, which did not have it).

Instead, since these use a nested contextmanager, pass through
and yield to the top-level run_tasks after the nested
contextmanager has finished (and thus run all the cleanup steps
in the subtasks for this test).

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
rgw tests: remove users after each test

These should all be cleanup up at some point. They're
almost all the same code.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>