improve /tests/ffi/memory

[pengshanyu]

When /tests/ffi/memory running on hardware, it occasionally fails during the disk_cleanup step.

[ INFO  ] PASS: Service QM is Active.
Failed to connect to system scope bus via local transport: No such file or directory
[ INFO  ] ffi-qm container inside qm is fully started
[ INFO  ] qm was started:  5s ago
[ INFO  ] ffi-qm was killed by SIGKILL
Mar 20 22:10:52 localhost systemd[1]: qm.service: A process of this unit has been killed by the OOM killer.
[ INFO  ] PASS: Command 'systemctl status qm --no-pager | grep "qm.service: A process of this unit has been killed"' successful
[ INFO  ] PASS: Command 'rm -rf ' successful
Error: OCI runtime error: crun: Runtime did not set up terminal
[ FAILED ] Error executing command 'podman exec -it qm /usr/bin/podman rm -af' with exit code: 255
Terminated

[pengshanyu]

Run into another new issue:

[ INFO  ] ffi-qm container inside qm is fully started
[ INFO  ] qm was started:  4s ago
[ INFO  ] ffi-qm was killed by SIGKILL
Mar 27 08:40:26 localhost systemd[1]: qm.service: A process of this unit has been killed by the OOM killer.
[ INFO  ] PASS: Command 'systemctl status qm --no-pager | grep "qm.service: A process of this unit has been killed"' successful
Error: no container with name or ID "qm" found: no such container
[ FAILED ] Error executing command 'podman exec qm /usr/bin/podman rm -af' with exit code: 125

It seems after a bad OOM, qm was not running, so podman exec qm … is invalid.

I will prepare another patch.