Remove stale files in /data/misc/virtualizationservice

[1] changed the UID of the virtualizationservice daemon and
/data/misc/virtualizationservice directory to `system`. However, this
can cause a permission denial issue when the directory has stale files
when the device was running a build before [1] and an OTA to [1] (or
above) is attempted. The daemon tries to delete the stale files - which
must have been still labeled as old UID and thus the daemon has no
privileged to delete them.

Fixing this issue by ensuring that the directory is always empty by
init.

[1] https://android-review.googlesource.com/c/platform/packages/modules/Virtualization/+/2059527

Bug: 230056726
Test: watch TH
Change-Id: I61c0297503347932b14b83859bec9ff82628336f