Improve robustness when migrating from appops xml

A device failing to create a complete appops.xml with all the
attributes needed will cause appops migration to fail when upgrading.

AppOpsService is reading its files as part of ActivityManagerService
start, which happens before rescue party is started.

Upon failure Rescue party is not started, there is no attempt to
reboot and the user is stuck with a device trying to boot.
A user experiencing this will think the device is bricked.

This change will log the actual error, treat the appops xml as not
existing instead of throwing an exception.

Bug: 323262109
Test: adb root
    adb shell stop
    adb shell rm /data/misc/apexdata/com.android.permission/access.abx \
        /data/misc_de/0/apexdata/com.android.permission/access.abx
    adb shell dd if=/dev/urandom of=/data/system/appops_accesses.xml \
        bs=4096 count=2
    adb shell dd if=/dev/urandom of=/data/system/appops.xml bs=4096 \
        count=2
    adb shell start
Change-Id: Ic24259662e1c7f0cfe23c72bd1c390f9aff80bec