In the error handling path, don't call close(fd) if the error we're

handling is that fd = open(foo) is -1.  This bug is harmless since
close(-1) just returns an error (which the code ignores).

Found by:	Coverity Prevent(tm)
CID:		1503 (in userland test run)

bin/rcp/rcp.c

@@ -403,7 +403,8 @@ syserr:			run_err("%s: %s", name, strerror(errno));
 		if (response() < 0)
 			goto next;
 		if ((bp = allocbuf(&buffer, fd, BUFSIZ)) == NULL) {
-next:			(void)close(fd);
+next:			if (fd >= 0)
+				(void)close(fd);
 			continue;
 		}