Add NetworkFactory names and unregistration.

Some Factories come and go (Telephony) and so they need to be able to unregister.
Also, debugging is tough when the factories are anonymous, so add names for logging.

Lastly, only send single set of NetworkRequests to a newly registered NetworkFactory
and only send the requests.

Change-Id: I717d63363f25c446f8ecf38d933b1a35d744af6e