Add tests for uninstalling while task is pinned

If the device is in locked task mode then package can't be uninstalled
because this might force the device out of the locked mode.

1. Test that the app can't be uninstalled if the app requests to be
uninstalled.
2. Test that an app can't uninstall another one using the
packageinstaller apis.
3. Test that an app can't be uninstalled using shell commands.

Test: These tests with and without the fameworks patch
Bug: 135604684
Change-Id: Ia6143a32770a87ec7ecffef0286062422aa0acfc