Fix the jetpack_site_icon_url to return a square when requesting the 512 image
Rebase, Only sync main_network_site when we update the plugin

Currently plugin_upgrade runs everytime,
So we use the general sync every option to ensure that
main_network_site gets pushed to .com
Merge pull request #1373 from Automattic/network-site-url-sync

Sync: Network site url sync