Resume interrupted restorecon in a separate thread.

The previous restorecon was interrupted. It's either crashed (unlikely), or the phone was rebooted. Possibly because it took too much time. This time let's move it to a separate thread - so it won't block the rest of the OS.

Fixes: 308541523
Test: presubmit
Change-Id: I523ab86dfa53180db1b58e5544a701144981152f