ssh: Fix type that broke offloading.

Reported by Simon Streit <simon@netpanic.org>.
Regression introduced in 3270308eeb.

* guix/ssh.scm (remote-daemon-channel)[redirect]: Unquote SOCKET-NAME.

guix/ssh.scm

@@ -268,7 +268,7 @@ EXP never returns or calls 'primitive-exit' when it's done."
 
        ;; Use 'connect-to-daemon' to honor GUIX_DAEMON_SOCKET.
        (let ((sock    (connect-to-daemon (or (getenv "GUIX_DAEMON_SOCKET")
-                                             socket-name)))
+                                             ,socket-name)))
              (stdin   (current-input-port))
              (stdout  (current-output-port))
              (select* (lambda (read write except)