Exclude default APN from unmetered bypassing check

Currently telephony will let unmetered APN type of
data setup no matter user enables or disables the data. This
creates confusion for users when default APN type (i.e. internet)
is unmetered. The user can still user interent even when data is
turned off.

Now exclude default APN type from unmetered bypassing check. Other
APN types (e.g. IMS) can still go through when data is off.

Test: Unit test + Manual
Fix: 152245363
Change-Id: If2cd5474ff356b3de0cc4e567eead4535c31c76a