DO NOT MERGE Disable app pinning when emergency call button pressed

Also disables app pinning when the "return to call" button is pressed
and brings up the in-call screen when app pinning is stopped if there is
an existing call.

Combination of ag/1091397 and ag/1085584 adapted for MNC.

Bug: 28558307
Bug: 28761672
Change-Id: I82ec4042bff387c845ce571b197a4a86e1dd5ec8