MXS-1300: Improve test coverage

The tests now cover 100% of all source files with the exception of the
call.js and common.js source files.

maxctrl/test/special.js

@@ -0,0 +1,20 @@
+require('../test_utils.js')()
+
+describe("Library invocation", function() {
+    before(startMaxScale)
+
+    var ctrl = require('../lib/core.js')
+    var opts = { extra_args: [ '--quiet'] }
+
+    it('extra options', function() {
+        return ctrl.execute('list servers'.split(' '), opts)
+            .should.be.fulfilled
+    })
+
+    it('no options', function() {
+        return ctrl.execute('list servers'.split(' '))
+            .should.be.fulfilled
+    })
+
+    after(stopMaxScale)
+});