Removed a check that every dependency of sockets.target has to be active

The assumption is not correct. We can't rely on it. Also fixed the
verify_results invocation to pass the correct amount of tests and defs.
Moved functions from systemdshared to the probes that use them
Fixed systemdunitproperty tests, default.target is an alias, not a unit name

There were other issues as well, the tests had human readable text in
@comment, verify_results expects true or false there.
Altered systemd probes tests to use -.mount instead of boot.mount

boot.mount needn't be enabled or even present on a fully functional
system.