Revert "Default AT&T tethering and MHS modes to off"

This reverts commit f0130356a775005cca71008b26a5ad4a0ca50bdb.

Conflicts:
	overlay/frameworks/base/core/res/res/values-
mcc310-mnc070/config.xml
	overlay/frameworks/base/core/res/res/values-
mcc311-mnc180/config.xml

Change-Id: I2fc7dda10b9dbbf19fc65a18922cfdb6291c5353