Add required flag to registerReceiver call in MetricsLogger

Android T adds support to allow a runtime receiver to be registered as
not exported, but to ensure apps can take advantage of this, calls to
registerReceiver must specify a flag indicating whether the receiver
should be exported for apps targeting T+ that are registering for
unprotected broadcasts. This commit adds the RECEIVER_NOT_EXPORTED
flag to the call to registerReceiver in MetricsLogger since this
action is only broadcast via a PendingIntent by the AlarmManager
so it will always appear as coming from the local UID.

Bug: 161145287
Test: Build
Change-Id: I9c8d1a3fd476ce50bb5d517c017d1465eeeb903e