Fix for OOIION-983, lost processes on reappearing eeagent not cleared.

Also includes a test for this problem
Make test_minimum_time_between_starts more likely to pass on busy
systems
Fix mock eeagent cleanup behaviour
Avoid throttling procs in missing ee test
Bigger timeout for missing_ee test
Give more time for test_missing_ee to pass
Make mock eeagent handle multiple procs with different rounds better
Avoid waiting for PENDING, since the notification can happen before we
check
Remove processes from assigned list when evacuating nodes
Retry clearing of resource assignments
Avoid letting engine4 scale down for test_missing_ee