If a relationship isn't defined, it should not be removed. Only if a
relationship is change to a null relationship, should it be removed.
Also fixed the maxctrl test suite to verify that both it and the REST API
tests pass.
Moved and renamed the starting and stopping scripts from the REST API
tests to a common directory. This way the MaxCtrl tests can use the same
scripts to start and stop MaxScale.
Also moved the test configuration file into the `test/` directory and
changed some of the default directory locations.
The script can now be used to run an arbitrary set of Node.js tests as
long as they define the `test` npm target. Refactored REST API tests to
fit into this framework.
