Fix toggleLastAppImpl
getRunningTasks causes an NPE. Switch to same behavior as RecentApplicationsDialog by using getRecentTasks and relaunching the last activity if it died.

Change-Id: I18b2b6711bc11f261ca2687a471a3e8bf984c705
Merge "Fix toggleLastAppImpl getRunningTasks causes an NPE. Switch to same behavior as RecentApplicationsDialog by using getRecentTasks and relaunching the last activity if it died." into android-4.4