mgr: load all modules (not just active ones)

mgr: load all modules (not just active ones)

This is to enable us to learn more about the module
before it is enabled, such as whether its can_run method
return true.

We can also use this to enable loading a module's
commands before it is enabled, to give the user
a better response when they try to use a command
belong to a module that is not loaded.

Signed-off-by: John Spray <john.spray@redhat.com>