In sigchild_handler(), finish with waitpid() before reinitializing

the SIGCHLD handling.

socket.c

@@ -431,10 +431,10 @@ int is_a_socket(int fd)
 
 static RETSIGTYPE sigchld_handler(UNUSED(int val))
 {
-	signal(SIGCHLD, sigchld_handler);
 #ifdef WNOHANG
 	while (waitpid(-1, NULL, WNOHANG) > 0) {}
 #endif
+	signal(SIGCHLD, sigchld_handler);
 }