More consistent right-now/footer messages related to version and upgrades in...

More consistent right-now/footer messages related to version and upgrades in multisite. propx SergeyBiryukov. fixes #15545

git-svn-id: https://core.svn.wordpress.org/trunk@18843 1a063a9b-81f0-0310-95a4-ce76da25c4cd