Hide work messages even when main user isn't secure

For example if user 0 has no lock screen set, but the work user does,
and the "hide all notifications while locked" field is set, we should
hide those notifications because they are supposed to be hidden behind
the work lock screen.

Fix: 32585026
Test: statusbartest/NotificationTestList.java
Change-Id: I29243f683fd4ef2d5fc71a40cd1e37ee29c5679c