services: Defer service delete until all handles are closed

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=7438

Your paranoid android.


=== w7u (32 bit service) ===
service.c:1381: Test failed: Something wrong in the calculation
service.c:1417: Test failed: Active services mismatch 1
The test timed out