Get fsid for daemons from asok (the true daemon field)

Sometimes fsid would appear to be full of 0s; we were getting it
from the ceph.conf value, which isn't required to be present.
Get it instead from the daemons themselves.

Signed-off-by: Dan Mick <dan.mick@inktank.com>
Fixes: #9639
Add flake8 testing for _modules; fix a couple of lint errors in ceph.py

Signed-off-by: Dan Mick <dan.mick@inktank.com>