Introduce the DeamonForm base class to cephadm.py and make various
daemon-type classes into fully fleged deamon form classes.
Some classes already had a semi-standard `init` classmethod for
instantiation. In these cases the new `create` classmethod is a thin
wrapper over the existing method. In cases where the class was not
already being instantiated a minimal set of methods are added.
Signed-off-by: John Mulligan <jmulligan@redhat.com>