Treat action=submit as 'alreadyediting'

This fixes an issue where action=submit users saw the one-button CTA.
They now see no CTA, just like action=edit.

When you do a GET request to action=submit, it treats it as an edit,
since there is no text submitted (used for preview or submit with POST
to action=submit).  However, wgAction is still 'submit'.

All returns to a returnto/returntoquery URL use GET.

Change-Id: I4ce1dd391c2aa6f8115991793f584a7c170210c1
Merge "Treat action=submit as 'alreadyediting'"