cephadm: combine deploy functions some more

cephadm: combine deploy functions some more

During review it was pointed out that much of command_deploy and
command_deploy_from were still common. Combine the bulk of
command_deploy and command_deploy_from into a new _common_deploy.
The old _common_deploy is renamed to _dispatch_deploy but kept
as a separate function.

The reason for keeping _dispatch_deploy as a function is that
it limits the scope of variables. It helps knowing exactly what
is needed and what is not needed from _common_deploy.

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