Update DPM unit tests checking isProvisioningAllowed for comp.

Two of the tests were actually checking the same thing. Removed one.
Refactore another test to make it easier to read.

Test: adb shell am instrument -e class com.android.server.devicepolicy.DevicePolicyManagerTest
-w com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
BUG:32629873

Change-Id: Id4ca9bd8c113a858b016fb02d04bf4c76bbcb027