Looks like it was people clicking google code's "export to github" feature before you got round to doing it ;-)
I wouldn't worry about it - the clones will probably not go anywhere and just die off, abandoned. True they don't link back to your now-canonical repo. As viraptor said, maybe contact the users. They might prefer to fork your repo now it's on github.
I have exported the project on github, but in the google code page, this button is still available and they don't provide by default any link or redirection to the new github repository exported by google tools. The google support suggests me to make an "url redirection" to different website, the github repository.
I wouldn't worry about it - the clones will probably not go anywhere and just die off, abandoned. True they don't link back to your now-canonical repo. As viraptor said, maybe contact the users. They might prefer to fork your repo now it's on github.