Use PM instead of PMI in DefGrantPolicy for simple cases

This is a step wowards eventually moving DPGP to a mainline module

Test: gts-tradefed run singleCommand gts -m GtsPermissionTestCases -t com.google.android.permission.gts.DefaultPermissionGrantPolicyTest
Change-Id: I81118bcad7faed8d72343cb81300d3478ee13838