Fix use of memorized phoneId.

We remember the phoneId we used to make the request so when the request is released we can
talk to the proper DcTracker even if the subId -> phoneId mapping is lost (removed the sim).
However the list of requests is a singleton and entries are stored per requestId so
a request that applies to multiple phones only has a single entry - we can't record
the phone id at request submission time.

Change it to store the phoneId at request execution time.  This also removes the need
for a separate "has been executed" boolean since we won't have an executed-phoneId if
it's not been executed.

In the future we should get rid of multiple TelephonyNetworkFactories, simplifying all
this.

bug:24411288
Change-Id: Ie430e0a9251c3ae09384e1a4e29b65fe90f46740