OOM-adjust an app to the foreground for startForegroundService

That is, OOM adjust it appropriately when the service is kicked off.
Previously it was mistakenly not recognizing the foreground intention
at the OOM level until the service called startForeground(), so there
was a period of inappropriate OOM vulnerability.

Bug 36990485
Test: manual

Change-Id: Ic9b56ef29d5120bf7912681900e9ebaeb0abc5d6