NEXUS-7789: Fixing IT and fixing bug it revealed

After fixing the ignored Nexus4066TaskMutualExclusionIT it
revealed that mutual exclusion is "less strict" that it should,
it does not consider transitive group members.

IT fixed and enabled, and bug fixed.
NEXUS-7789: Fix YUM related tasks
Merge remote-tracking branch 'origin/master' into NEXUS-7789-bug-not-considering-gofgs
NEXUS-7789: Improve reliability of TP Provider
NEXUS-7789: Proper resubmission of already running task

As YUM depends on this, and UT actually depends on proper
functionality.
NEXUS-7789: Simplified based on Stuart's comment
Merge pull request #910 from sonatype/NEXUS-7789-bug-not-considering-gofgs

NEXUS-7789: Fixing IT and fixing bug it revealed