container: force rm --storage on ExecStartPre

container: force rm --storage on ExecStartPre

This is a workaround to avoid error like following:
```
Error: error creating container storage: the container name "ceph-mgr-magna022" is already in use by "4a5f674e113f837a0cc561dea5d2cd55d16ca159a647b7794ab06c4c276ef701"
```

that doesn't seem to be 100% reproducible but it shows up after a
reboot. The only workaround we came up with at the moment is to run
`podman rm --storage <container>` before starting it.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1887716
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>