Merge pull request #18521 from etiennesegonzac/bug-997924-callscreen-fix-visibility

Bug 997924 - Make sure the preloaded callscreen doesn't keep an audio channel open
Conflicts:

	apps/callscreen/js/index.js
	apps/system/js/dialer_agent.js
Merge pull request #18574 from leonazhao/bug997924v1.3t

Bug997924v1.3t