vendor: Allow devices to set the GMS client id

This will look for flags in omni_<device>.mk, if none preset, use ro.com.google.clientidbase=android-google

Conflicts:
	config/common.mk

Change-Id: I42957104837b96ea24e485c8dd2e6332ff42d5b7
Merge "vendor: Allow devices to set the GMS client id" into du44