Improved dumpsys device_policy:

- Used IndentingPrintWriter from the proper package (it was using a
  deprecated version).
- Wrapped the IndentingPrintWriter in a try-with-resources block.
- Added some missing state.

Test: adb shell dumpsys device_policy
Bug: 171517112

Change-Id: I946f7f2b1a6151230f3cf752558ee1aa6a05ad2b