Add support for RHEL7

Add support for RHEL7 which uses dconf instead of gconftool-2. 

Reviewed by: Swapna Krishnan <skrishna@redhat.com>
Currently, these tests can only be run on RHEL6 guests. I'm working on adding support for RHEL7 guests and in future, for Fedora guests. You cannot run these tests on other guests at this point. 

I can add a try except block to catch situations in which the file is not present and log a message saying this test is not supported on those other OSs. 

Would that be ok?