az container stop seems to send SIGKILL rather than SIGTERM

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**Describe the bug**

When executing _az container stop -g foo -n bar_ I noticed that the stop units are killed in the middle of its execution. This happens in a CentOS image. When logging in to the container and sending a SIGTERM to the PID-1, then every of the specified stop units get properly executed. I therefore conclude that _az container stop_ sends a SIGKILL to the PID-1 process, does not implement a graceful shutdown

**To Reproduce**

_az container stop ..._

**Expected behavior**

_az container stop_ to send a SIGTERM to the PID-1 process of the container, i.e. _ACI_ should implement a graceful shutdown and only after a specified amount of time a SIGKILL should follow

**Environment summary**

Azure ACI with a CentOS based image

**Additional context**