frameworks/base: Fix delay in sending AUDIO_BECOMING_NOISY intent

AUDIO_BECOMING_NOISY intent is sent as background intent which causes
delay in receiving pause event. This delay caused audio leak. By
marking the event as FLAG_RECEIVER_FOREGROUND, this intent is
received sooner by Application.

Change-Id: Ib978cf8322dcddbc01f59824f95fa7800f9c35af
CRs-Fixed: 652549

Patchset: 1
http://review.cyanogenmod.org/#/c/74280/