ConfigContext config set cannot be run multiple times in one scenario

[upchuk]

The ConfigContext::setConfig() keeps a backup of the config that we set. However, if we need to set it multiple times in the same scenario the backup is overridden by the last time it runs. The fix is pretty simple: check if the backup has already been made already before setting it.

[pfrenssen]

This looks good to me. Thanks for the contribution!

Looking at this code I am thinking that the setConfig() method should be made protected. The public version of this is called setBasicConfig() and has a step definition associated with it. I will make a followup for this.