Switch to mkisofs for openSUSE distributions

In Tumbleweed genisoimage was dropped in favor of cdrtools,
so installing that no longer works. We can however install
mkisofs directly and switch to that as that is also available
in Leap 42.3 and Leap 15.0+ family distros.

Also drop dependency on libmysqlclient-devel which appears
unnecessary (and is no longer available with mariadb 10.2+)

Change-Id: Ie8402204b6cdf94c21865caba116d3fd1298c5ad
diff --git a/lib/nova b/lib/nova
index 2eef8c4..939806f 100644
--- a/lib/nova
+++ b/lib/nova
@@ -506,6 +506,12 @@
     if [ "$FORCE_CONFIG_DRIVE" != "False" ]; then
         iniset $NOVA_CONF DEFAULT force_config_drive "$FORCE_CONFIG_DRIVE"
     fi
+
+    # nova defaults to genisoimage but only mkisofs is available for 15.0+
+    if is_suse; then
+        iniset $NOVA_CONF DEFAULT mkisofs_cmd /usr/bin/mkisofs
+    fi
+
     # Format logging
     setup_logging $NOVA_CONF