Move REST API test scripts into a common directory

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.

test/run_npm_test.sh

@@ -82,6 +82,9 @@ do
     echo "Done!"
 done
 
+# Make sure no stale processes of files are left from an earlier run
+./stop_maxscale.sh
+
 # Run tests
 npm test
 rval=$?