mysql_install_db: clarify the after-install message

don't tell users to set the root password if they're using unix_socket

scripts/mysql_install_db.sh

@@ -525,6 +525,9 @@ then
   s_echo "To start mysqld at boot time you have to copy"
   s_echo "support-files/mysql.server to the right place for your system"
 
+  if test "$auth_root_authentication_method" = normal
+  then
+    echo
     echo
     echo "PLEASE REMEMBER TO SET A PASSWORD FOR THE MariaDB root USER !"
     echo "To do so, start the server, then issue the following commands:"
@@ -538,6 +541,8 @@ then
     echo "which will also give you the option of removing the test"
     echo "databases and anonymous user created by default.  This is"
     echo "strongly recommended for production servers."
+  fi
+
   echo
   echo "See the MariaDB Knowledgebase at http://mariadb.com/kb or the"
   echo "MySQL manual for more instructions."