Add "failed_when" condition for "dblab_reload" handler

Ignore the missing container error.
It makes sense during the initial deployment when the handler was started before the container was created.

Fixed:

fatal: [10.172.0.20]: FAILED! => {"changed": true, "cmd": ["sudo", "docker", "exec", "dblab_server", "kill", "-SIGHUP", "1"], "delta": "0:00:00.026912", "end": "2024-01-25 15:20:55.193292", "msg": "non-zero return code", "rc": 1, "start": "2024-01-25 15:20:55.166380", "stderr": "Error response from daemon: No such container: dblab_server", "stderr_lines": ["Error response from daemon: No such container: dblab_server"], "stdout": "", "stdout_lines": []}
RUNNING HANDLER [zpool : Reload DBLab Engine to apply configuration changes] ***

https://gitlab.com/postgres-ai/dle-se-ansible/-/jobs/6013075402