(RE-2368) Update for CentOS 7

We can now remove the bandaids because CentOS 7 has been officially
released. This consists of removing the bandaid files themselves and
updating the mocks to remove lingering patch code. We also have updated
the pe-el-mock-config template to pull from osmirror instead of yo.
What is this used for again? If it's used for PE 2.5, we shouldn't need it, right? We don't support rhel7 for PE 2.5.....