Remove unused code and cleanup parameters for DPM dev ID access

Fixes: 123684619
Test: cts-tradefed run cts-dev -m CtsDevicePolicyManagerTestCases -t \
      com.android.cts.devicepolicy.DeviceOwnerTest#testDeviceOwnerCanGetDeviceIdentifiers
Test: cts-tradefed run cts-dev -m CtsDevicePolicyManagerTestCases -t \
      com.android.cts.devicepolicy.ManagedProfileTest#testProfileOwnerCanGetDeviceIdentifiers
Test: cts-tradefed run cts-dev -m CtsDevicePolicyManagerTestCases -t \
      com.android.cts.devicepolicy.ManagedProfileTest#testProfileOwnerCannotGetDeviceIdentifiersWithoutPermission
Test: cts-tradefed run cts-dev -m CtsDevicePolicyManagerTestCases -t \
      com.android.cts.devicepolicy.DeviceOwnerTest#testDeviceOwnerCannotGetDeviceIdentifiersWithoutPermission

Change-Id: Ibc647847a47911c0c32cf5cf33bd3187dc3aebd2