config keys are always merged, even if we want to overwrite

[johnynek]

https://groups.google.com/forum/?fromgroups#!topic/cascading-user/Bvev1F8ZVOM

If a key is already set by an incoming Config, it looks like there is no way to overwrite it. The API should allow this.

[johnynek]

https://github.com/twitter/scalding/blob/master/src/main/scala/com/twitter/scalding/Mode.scala#L102

That's the problem: we are always calling unionValues.

[johnynek]

This was fixed. Now you override the config method in your job:

https://github.com/twitter/scalding/blob/develop/src/main/scala/com/twitter/scalding/Job.scala#L100

Look at the incoming mode.config, and choose how to update it.