Do not install mysql if mariadb is installed on openSUSE

mariadb and mysql are conflicting on a package level, but are compatible
for our needs. So if mariadb is already installed, do not try to install
mysql.

Change-Id: I3aa991c1c4691df3e3f4798505668da3ab908998
Merge "Do not install mysql if mariadb is installed on openSUSE"