Non-priv apps are not allowed to use always/never lock task mode

It worked oppositely since 2bf28320.

Bug: 162808850
Bug: 158833495
Test: atest ActivityRecordTests
Change-Id: Ic5f1b1531816a90ff341597e6d012a6c62c04480
Merged-In: Ic5f1b1531816a90ff341597e6d012a6c62c04480
(cherry picked from commit 3d494aad)