Container pidfile not being overridden correctly

[TeknoVenus]

When starting a container with the --pid-file argument, if the file already contains data it will only be partially overridden with the containers PID.

This causes an issue if restarting a container and using the same pid file if the new container gets assigned a PID with less digits.

Example:

• PID file does not exist. Container starts and is assigned the PID 21948. 21948 is written to the pidfile correctly
• Stop and restart the container using the same pidfile. Container is now assigned the PID 7694. The pid file now contains 76948, which is incorrect. The file should just contain 7694

Obviously we could work around this and ensure the pidfile was deleted every time the container stops, but crun should override the entire file with the new PID instead of just overriding the number of digits it needs to and leaving the rest.

Crun version: 0.14.1

[giuseppe]

opened a PR here: #505