Remove unreachable code, and don't leak contexts

This patch performs some minor cleanups for things detected by "go vet":

 - Remove one line of unreachable code.
 - Don't leak contexts until their deadline expires, cancel them.

chasquid.go

@@ -372,8 +372,6 @@ func (s *Server) serve(l net.Listener, mode SocketMode) {
 		}
 		go sc.Handle()
 	}
-
-	l.Close()
 }
 
 type Conn struct {