cli: Add module refresh command

Adds a command to the CLI to unload and then
load a module. This makes it easier to perform
these operations which are often done
subsequently to load a new version of a module.

"module reload" already refers to reloading of
configuration, so the name "refresh" is chosen
instead.

ASTERISK-29807 #close

Change-Id: I595f6f11774a0de2565a1fba38da22309ce93a2c