updating yum distributor to include metadata checksum in repodata filena...

...mes

https://rally1.rallydev.com/#/7675694122d/detail/userstory/17378719876

Initially, I was calculating checksum for each repodata file as it was getting generated. Since we calculate it and update repomd.xml file in the end anyway, I am leveraging that and then renaming the original repodata file with checksum included.