Added check of ActivityInfo launch mode when starting activity.

When starting a singleTop activity from a singleInstance activity,
the onNewIntent() callback was not called when expected. The
reason for this was that only the launchMode specified on the
intent was checked and not the launchMode specified in the manifest.

Fixes issue 17137.

Change-Id: I1a9bc1007d6f5145bf93a6161534732bf5214b7a