micro-ROS agent stops on logger setup line

- Hardware description: micro-ros node: STM32L4 Discovery kit IoT node (B-L475E-IOT01A2), agent: Raspberry Pi 4 Model B 2GB RAM
- RTOS: Zephyr
- Installation type: micro_ros_setup
- Version or commit hash: humble

#### Steps to reproduce the issue

1. Configure firmware to use ping-pong demo application and usb-serial transport.
2. Build and flash.
3. Plug microcontroller into Raspberry and run micro-ros agent.

#### Expected behavior
Micro-ros node starts properly and its topics are visible from Raspberry.

#### Actual behavior
Micro-ros agent stops on:
```
[1667242557.691466] info | TermiosAgentLinux.cpp | init | running... | fd: 3
[1667242557.692280] info | Root.cpp | set_verbose_level | logger setup | verbose_level: 4
```

#### Additional information
I tried to unplug, then plug in the board and resetting it with dedicated pushbutton.
Raspberry runs ROS2 Humble on Ubuntu 22.04 server with kernel:
`Linux ubuntu 5.15.39-rt42-raspi #1 SMP PREEMPT_RT Sat Jul 16 08:34:58 UTC 2022 aarch64 aarch64 aarch64 GNU/Linux`

未指定源文件或测试。首先使用 STM32L4 Discovery kit、Zephyr、USB-serial transport 以及 Raspberry Pi 上的 micro-ROS agent 重现该问题，然后检查 agent 启动路径中与报告的 logger setup 输出相关的部分。完成的标准是 agent 保持运行，并且可以从 Raspberry Pi 看到该节点的 topics。

由索引模型根据 Issue 内容生成。