Don't deactivate a plugin that is both network activated and activated on the...

Don't deactivate a plugin that is both network activated and activated on the main site after editing. Props SergeyBiryukov. fixes #16011

git-svn-id: https://core.svn.wordpress.org/trunk@17183 1a063a9b-81f0-0310-95a4-ce76da25c4cd