psql: Set up cancel handler later

The cancel handler was uselessly set up even before the first connection
was opened.  By setting it up afterwards, the user can use Ctrl+C to
abort psql if the initial connection attempt hangs.
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Reviewed-by: Ryan Kelly <rpkelly22@gmail.com>

src/bin/psql/startup.c

@@ -111,8 +111,6 @@ main(int argc, char *argv[])
 	setvbuf(stderr, NULL, _IONBF, 0);
 #endif
 
-	setup_cancel_handler();
-
 	pset.progname = get_progname(argv[0]);
 
 	pset.db = NULL;
@@ -246,6 +244,8 @@ main(int argc, char *argv[])
 		exit(EXIT_BADCONN);
 	}
 
+	setup_cancel_handler();
+
 	PQsetNoticeProcessor(pset.db, NoticeProcessor, NULL);
 
 	SyncVariables();