Use locale language instead of harcoded langauge

Used the locale language instead of the hardcoded language since
ISO 639 is not a stable standard. Some language codes changed before.

This is part of the cell broadcast language filtering feature
added per U.S. FCC requirement.

Test: Manual
Bug: 110754638, 71497689, 110896497
Change-Id: I3cf42eb037cdbb40597c1053fedb36b478277fc9