Mariadb changed format for RHEL repository

[Sewanee-raval]

Mariadb has changed their format for RHEL repos.
They now request that we use the following format in the rhel (and clone) repository files.

# MariaDB 10.11 RedHatEnterpriseLinux repository list
[mariadb]
name = MariaDB
baseurl = [https://rpm.mariadb.org/10.11/rhel/$releasever/$basearch]
gpgkey = https://rpm.mariadb.org/RPM-GPG-KEY-MariaDB
module_hotfixes = 1
gpgcheck = 1

Their change is from yum.mariadb.org to rpm.mariadb.org and how they want the baseurl format.
The current method will often result in an metadata error when yum or dnf tries to update the repo.

I will submit a pull request once I have figure out how to do it.