Use mysqladmin status instead of ping to check server

The ping does return 0 even in case it can not connect to the server.

Signed-off-by: Michal Čihař <michal@cihar.com>

demo/maintenance/mysql-tester

@@ -7,7 +7,7 @@ if [ -z "$1" -o -z "$2" ] ; then
 fi
 
 # Test Debian maintenance user
-if ! ssh demo-$1 /usr/bin/mysqladmin ping ; then
+if ! ssh demo-$1 /usr/bin/mysqladmin status ; then
     exit 1
 fi