try to improve display


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@19919 35612d4c-9d10-0410-837c-bf9dd1be60d7
do not display network dropdown (only for information) on network port form.
Are you agree ?
see http://www.glpi-project.org/forum/viewtopic.php?id=31031


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@19920 35612d4c-9d10-0410-837c-bf9dd1be60d7