Expertise API: don't let create a new job is there one already running with the same configuration

[melisabok]

I think we should protect our API and don't let PCs to compute the scores for the same group more than once at the same time.

Sometimes they compute the setup matching without waiting for the process to complete. I suggest the API should validate if there is a job with the same request already running then throw an error and ask the user to wait until the existing job that is running to complete. Thoughts @haroldrubio @carlosmondra ?

[carlosmondra]

I thought we were already doing this. Definitely, we should ask them to wait for the process to complete.