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