Update znapzendzetup.pod

Fix mysql kill child
#642

doc/znapzendzetup.pod

@@ -255,7 +255,7 @@ e.g. for database locking/flushing (pre) and unlocking (post).
 If you deal with a mariadb/mysql database, you can use
 
   pre-snap-command  = /opt/oep/mariadb/bin/mysql -e "set autocommit=0;flush tables with read lock;\\! /bin/sleep 600" &  /usr/bin/echo $! > /tmp/mariadblock.pid ; sleep 10
-  post-snap-command = /usr/bin/kill `/usr/bin/cat /tmp/mariadblock.pid`;/usr/bin/rm /tmp/mariadblock.pid
+  post-snap-command = /usr/bin/pkill -P `/usr/bin/cat /tmp/mariadblock.pid`;/usr/bin/rm /tmp/mariadblock.pid
 
 to make sure that the on-disk data is consistent when snapshotting. The
 lock stays in place only for the duration of the lingering connection