Issue with gluster-file-system azure template

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[Template Name goes here](Template link goes here)

### Issue Details
gluster-file-system azure template
https://github.com/Azure/azure-quickstart-templates/tree/052db5feeba11f85d57f170d8202123511f72044/gluster-file-system

### Repro steps (*if necessary, delete otherwise*)
1.The path to fetch gluster packages is no more valid for CentOS. I have not tested for ubuntu yet.
2.Can we also include CentOS 7 as the default version of OS ?
3.Can the template be updated to use managed storage ?

Inspect the gluster-file-system template at the linked repository path and first reproduce deployment to confirm the CentOS package URL failure. Review how the template selects the OS version and storage, then verify that the package source works and assess the requested CentOS 7 default and managed storage changes.

Written by the indexing model from the issue text.