Bug#26446321 CONTRIBUTION: FIX INSTALL DATABASE BY USED MYSQLD --INITIALIZE

Since MySQL 5.7 mysql_install_db has been deprecated, mysqld --initialize is
now preferred. Switch mysqld_multi.sh.

Based on contribution from tigerb, bug#87080.

Change is 5.7 specific, MySQL 8 was fixed by:
 WL#9071: Remove mysql_install_db and server --bootstrap option

Author: trosten

scripts/mysqld_multi.sh

@@ -340,7 +340,8 @@ sub start_mysqlds()
         if (! -d $datadir."/mysql") {
           if (-w $datadir) {
             print "\n\nInstalling new database in $datadir\n\n";
-            $install_cmd="@bindir@/mysql_install_db ";
+            $install_cmd="@bindir@/mysqld ";
+            $install_cmd.="--initialize ";
             $install_cmd.="--user=mysql ";
             $install_cmd.="--datadir=$datadir";
             system($install_cmd);