Handle or voidify all calls to close_all_fds()

In activate, it is important that we close the fds. In other cases, meh.

src/basic/process-util.c

@@ -1001,7 +1001,7 @@ _noreturn_ void freeze(void) {
         log_close();
 
         /* Make sure nobody waits for us on a socket anymore */
-        close_all_fds(NULL, 0);
+        (void) close_all_fds(NULL, 0);
 
         sync();