Make "security required" notification ongoing

* While investigating the referenced bug, it was discovered that
  canceling the "security required" notification (with "X", rather
  than the "cancel" option in the dialog) causes the notification
  to be unavailable until a reboot
* This puts the account needing a security update in the position
  of being unsyncable, and might explain the referenced bug (we
  have no confirmation of that step; on the other hand, the tester
  can't now reproduce the problem, so an unusual action like this
  is to be expected)
* The fix consists of making this particular notification "ongoing",
  which prevents the user from dismissing it; arguably, this should
  always have been the case anyway...
* Consider this fix for backport into LTE and MR2 branches

Bug: 5072343
Change-Id: Ia7419236cf9389380d1e079b1a9a6f425015c487
1 file changed