MaxScale docker image does not work

Due to changes that have happened in the code after the writing of the docker image, using the image as it is is not possible.

To prevent these sorts of problems, the image could simply install the latest MaxScale binary.

-- Could not find Node.js

CMake Error at maxctrl/CMakeLists.txt:20 (message):

  Not building MaxCtrl: npm or Node.js >= 6.0.0 not found.  Add the following

  to skip MaxCtrl: -DBUILD_MAXCTRL=N