Rename network admin submenus to not clash with top level menus. Props...

Rename network admin submenus to not clash with top level menus. Props ocean90, markmcwilliams. see #17378

git-svn-id: https://core.svn.wordpress.org/trunk@18026 1a063a9b-81f0-0310-95a4-ce76da25c4cd