Clear policy cache during DO removal

Remove left-over polices (such as mCanGrantSensorsPermissions)
from the cache so it's not interfering with subsequent test runs

Bug: 187862351
Bug: 184079462
Bug: 183162232
Bug: 183162329
Test: 1. atest MixedDeviceOwnerTest#testGrantOfSensorsRelatedPermissions
      2. atest MixedProfileOwnerTest#testGrantOfSensorsRelatedPermissions
Change-Id: I8551fca161c7df39228587a024f468a496dcdb58