R1:a85452b8d6ec

Allow daemons to be terminated in the absence of MySQL

Summary: Fixes T6842. Allow the daemons to always be terminated, even if MySQL is down. I was hoping to be able to optionally enable this behavior with the `--force` flag, but this seems messy.

Test Plan:
```lang=bash
> ./bin/phd start
Freeing active task leases...
Freed 1 task lease(s).
Preparing to launch daemons.
NOTE: Logs will appear in '/var/tmp/phd/log/daemons.log'.

Starting daemons as phd
Launching daemon…