Redirect to SpecialPage if nothing to do

If the user logged into Google account and is already logged in with the
connected wiki user, don't show only the Unlink-Button, redirect to
Special:GoogleLogin.

Bug: 67186
Change-Id: I309b33c5bde3c3dd8c4b0b3674c23905de9a6ed7
Merge "Redirect to SpecialPage if nothing to do"