Enable extservices tests to generate android-mts-extservices as well as android-mts. Bug: 170318013 Test: built locally and verified contents. Change-Id: I48e48bdee8957ebbd4c5c3db95854fc0a0cdb13d Merged-In: I48e48bdee8957ebbd4c5c3db95854fc0a0cdb13d Exempt-From-Owner-Approval: approved by owners in downstream branch.