Could not enable data connection

Could not enable the default type APN in below case:
1. Default apn exists, connect wifi
2. Delete default apn
3. Disconnect wifi

enableApnType won't reactivate default apn type when no
default apn exists. Add default apn criterium to avoid this.

Change-Id: Ic8699669e576e5d2140852f359e34ed6c3275633
SamsungQualcommRIL: Add more validation of Signal Strength

Change-Id: I4b166543ba6898616c9e64a86ff65693f8e33f72