Resync with Telephony after losing Phone service.

Bug shows we lost contact with the phone service.  We used to leave the notion of enabled alone
in this case, but that can lead to being out of sync (the mobile data connection may be
alive or come alive but if we think it is dead we ignore it).  Changing our
notion of its enabled-ness to 'enabled' means we'll pay attention to its messages going forward,
and since after a reboot it starts enabled we'll actually be in sync.

bug:2323057
Change-Id: Ie080b50d764e6879e712507aceb68f585f12f94e