Bug 1010418 - Answering a call from the Lockscreen then adding a contact to the call will bring the user to the homescreen

Revert "Merge pull request #17230 from snowmantw/issue982530-workaround"

This reverts commit 712846a016f807de4a8e6823bbf468c3a220ac0a, reversing
changes made to ed572dfcbee138edbc9483d41cb67a5128852313.

Conflicts:
	apps/system/js/lockscreen.js
Merge pull request #19463 from Rik/1010418-backout

Bug 1010418 - Answering a call from the Lockscreen then adding a contact to the call will bring the user to the homescreen r=me because backout.