vm/adb does "rm -Rf /data/syzkaller*" between reboots:

rm can't remove everything and it started failing recently after cgroup changes:

2021/10/18 12:20:27 failed to create instance: failed to run ["adb" "-s" "localhost:34369" 
rm: /data/syzkaller-testdir107020063/syzkaller.kw5FVG/233/cgroup: No such file or directory
rm: 233: Directory not empty

#2827 fixes this by unlinking symlinks.
But we need to do this for other VM impls (not really specific to adb) and use the more comprehensive executor remove_dir logic:

I think we need remove these dirs as part of executor "setup" invocation (it runs exactly once after boot). We probably need a separate setup verb ("purge") because some tools (syz-execprog?) may not need this on every invocation.