Cleanup setting fast abort
Adds count of tasks with missing stdout, input or output files.
Fast abort only consider average with succesful tasks.
remove dangling stats->total_tasks_failed
Use only execute and transfer time of succesfull tasks
Add flag to recognize foreman more easily
Do not fast abort foremen
Merge pull request #391 from btovar/fast_abort_mods

Fixes for WQ fast abort:
1. Use average of the running time of successful tasks when doing fast abort.
2. Don't fast abort a foreman.