broadband-modem-mbim: reload registration/location info after enabled

Until now we were fully discarding all registration updates happening during the "enabling" process, which is very unfortunate, because it meant we could be fully registered, but not reporting it like that because we missed the messages.

Fix this in the MBIM implementation, by making sure we don't attempt to apply the registration updates if we're enabling, and instead schedule an update of the same to be done as soon as we're fully enabled.

The Simple.Connect() logic is also updated to insert a 100ms wait that will allow us to make sure the enabled->registered transition happens right away, and so we "save" a MBIM automatic registration attempt that was incorrectly triggered.

Fixes #479 (closed)