Consider speeding up of RunTests script

[amyasnikov]

Splitting the work among multiple RQ workers may sufficiently reduce tests execution time for a huge amount of devices.

[amyasnikov]

It seems that the right approach of splitting the work among multiple workers involves changing the way the job is being triggered (I mean using depends_on RQ feature). It cannot be distinguished using NetBox Custom Scripts. It leads to throwing away Custom Scripts and implementing the same functionality using custom views and plain RQ.