TelephonyManager: isSmsCapable: respect telephony properties

The 2 telephony properties override if SMS send/receive is enabled
in the telephony code. Also respect them for the isSmsCapable API.

Use case: Acer A700/701 (Wi-Fi only/3G) share the same build

Change-Id: Iaa1b45c62fa5a48a4c4a222d5e47980dd1678d4