Prevents WearableExtender test from running on low API levels

WearableExtender doesn't support API 15 - this prevents failing tests
from running on <17 devices

This also adds a test which verifies WearableExtender is a no-op on
API <17

Bug:34808243
Change-Id: Icc4d65e38b687cee1b0249604f4f722173170f57
Fixes:34808243
Test: Ran manually on api 17 & api 15 emulators
1 file changed