MDEV-426: mariadb-service-convert to use MYSQLD_OPTS

During the review process OPTIONS was converted to MYSQLD_OPTS.
In the script mariadb-service convert, the ExecStart of the system
also uses this setting.

scripts/mariadb-service-convert

@@ -73,7 +73,7 @@ fi
 
 if [[ "${numa_interleave}" -gt 0 ]]; then
   echo
-  echo ExecStart=numactl --interleave=all ${cmd} '${OPTIONS}'
+  echo ExecStart=numactl --interleave=all ${cmd} '${MYSQLD_OPTS}'
   echo
 fi