ueventd: call _exit for safety

Make sure to call _exit instead of exit to avoid triggering exit
handlers that may have existed in the parent process.

Print out a log message when forking to process firmware events fails.

Change-Id: I2436bdf85d9a8ea26b718e62023f1dac89864667

init/devices.c

@@ -938,7 +938,9 @@ static void handle_firmware_event(struct uevent *uevent)
     pid = fork();
     if (!pid) {
         process_firmware_event(uevent);
-        exit(EXIT_SUCCESS);
+        _exit(EXIT_SUCCESS);
+    } else if (pid < 0) {
+        log_event_print("could not fork to process firmware event: %s\n", strerror(errno));
     }
 }