SettingsProvider: It maybe generated an error settings_ssaid.xml.fallback file...

SettingsProvider: It maybe generated an error settings_ssaid.xml.fallback file from the original xml.

For unknown reasons, when settings_ssaid.xml write interruption cause the file does not complete, then WriteFallbackSettingsFilesJobService starts, it will copy the error original file to settings_ssaid.xml.fallback directly. The next time Android restarts, it will fail to boot up because settings_ssaid.xml and settings_ssaid.xml.fallback cannot be parsed and loaded.

It is necessary determine whether the original file(etc:settings_ssaid.xml) integrity in SettingsProvider.java# writeFallBackSettingsFiles(settingsFiles)method.

FLAG: EXEMPT bug fix
Test: atest
Bug:419113196
(cherry picked from https://android-review.googlesource.com/q/commit:883afa96eda8063e2682c2cc22a2f75d975f60e4)
Merged-In: I9ce0952b3707279aed7b43b6d7f5056ce29f2861
Change-Id: I9ce0952b3707279aed7b43b6d7f5056ce29f2861