Modify the deprecation of PhoneNumberUtil isEmergencyNumber

1) Telephony API is still called by a bunch of Util methods in Android that
don't have context, therefore the service can be null. Throwing an
 exception can cause crash.
2) Fix the usage of isEmergencyNumber and isPotentialEmergencyNumber.

Test: Manual
Fixes: 129721537
Change-Id: If82bfc5102a9ac1d7e07ff744c0775a1dc95ba2c
Merged-In: If82bfc5102a9ac1d7e07ff744c0775a1dc95ba2c
(cherry picked from commit c6d55453)