[build] el6: make consistent quotes/el6 for EL6 OS test.
[build] el6: make consistent quotes/el6 for EL6 OS test.

OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS