Safecty checker improvements on DevicePolicyManagerService.

- Include mSafetyChecker on dump().
- Change OneTimeSafetyChecker so it's disabled after any operation.
- (Conditionally) log the mSafetyChecker used.

Bug: 172376923

Test: adb shell dumpsys device_policy | grep mSafetyChecker
Test: atest CtsDevicePolicyManagerTestCases:DeviceOwnerTest#testDevicePolicySafetyCheckerIntegration_allOperations,testDevicePolicySafetyCheckerIntegration_isSafeOperation,testDevicePolicySafetyCheckerIntegration_unsafeStateException \
  CtsDevicePolicyManagerTestCases:ProfileOwnerTest#testDevicePolicySafetyCheckerIntegration_allOperations,testDevicePolicySafetyCheckerIntegration_isSafeOperation,testDevicePolicySafetyCheckerIntegration_unsafeStateException

Change-Id: Ife936cea89c6e21a56454766ecb4b29b652bd584