Catch IOException when failed to parse new fields.

When parsing from a XML file written by previous code, the new fields
will get an IOException, catch the IOException and let the new fields
to have default value.

Change-Id: I2b2a494bf17aaf1383a6cc469d9c2addd6cac9c3
Fix: 119822293
Test: test com.google.android.gts.backup.UsageStatsRestoreHostSideTest#testUsageStatsRestore