cephadm: update additional container daemon form base class methods

cephadm: update additional container daemon form base class methods

Fix the function signature for the previously added stub
customize_container_args.
Add methods for customize_process_args and customize_container_envs.
The "process args" are args passed to the daemon process / entrypoint.
Container args are passed to the container engine.
Add a default_entrypoint method to return the default entrypoint for
a particular daemon-in-container.

Signed-off-by: John Mulligan <jmulligan@redhat.com>