Fix duplicate logCollect tar name

Going through some log archives stored at castor with @juanfmx2, we found that we have been creating duplicate names for log archives when a workflow run in more than 1 agent. 
The problem is that the tar archive name is like: workflow_name-task_name-counter-log.tar
So if 2 agents are running the same log collect task for a given workflow, we end up re-writing the log archives at castor :( as the agent don't know about each other counter.
This is one example:
http://vocms235.cern.ch:5984/wmagent_jobdump%2Fjobs/_design/JobDump/_show/jobSummary/425246
http://vocms216.cern.ch:5984/wmagent_jobdump%2Fjobs/_design/JobDump/_show/jobSummary/948384
@ticoann we could add the hostname in the tar archive name, and it should avoid the same problem again. Does it makes sense?