Fix segfault when worker sends an available results message and terminates.
The segfault happens because WQ does not remove the worker from the list of
workers with available results.

To make the removal in O(1) use a hash table instead of a list.
Remove worker entry from available_results after
retrieving the results of its task(s).
Bump to 4.1.0rc4
gpu_detection fixes
Bump to 4.1.0rc5
bugfix: Print exit_status even when it is zero
bugfix: submission scripts correctly escape arguments quotes
Bump to 4.1.0rc6
Add request_* resources to condor submit file
cvmfs disable alien cache
Bump to 4.1.0rc7