Revert "WIP: Domain Controller Role"

This reverts commit 228e849eee51d4d94f929e5b6587192f6bcb6868.

Accidentally pushed too soon.
Set persistent flag for instances also
Make auto-termination working within RoleBase and DBusRole also
Implement starting and stopping services, and use it in databaseserver.

Includes some work-in-progress edits to databaseserver, IMHO harmless enough but will split them if asked.

Now rereading this, should the StartUnit/StopUnit D-Bus calls be non-blocking as well?  At this late hour I’m inclined to say that they are explicitly designed to be returning quickly, so it isn’t really necessary.

Testing Done:
starting/stopping postgres through d-feet.

Reviewed at https://reviewboard-fedoraserver.rhcloud.com/r/54/
Fix minor typo in async_test
Add asynchronous helper for calling a subprocess

This will spawn a thread to monitor the subprocess, capture both
stdout and stderr and throw an exception if the process terminates
with a non-zero error code.
WIP: Domain Controller Role