Clear updated font files in safe mode.

Bug: 176939176
Bug: 181536798
Bug: 187190639
Test: atest FrameworksServicesTests:UpdatableFontDirTest
Test: atest UpdatableSystemFontTest
Test: manually triggered safe mode and confirmed updated fonts are
      removed.
Change-Id: I946a7df383a27bbfda2931a916ca28d8ee14feb6
5 files changed