fix: fix docker pull fallback when podman fails or is not being used

[reubenmiller]

Fix an issue with the fallback logic when running on docker (instead of podman).

The bug previously assumed podman was always available (due to an inverted check).

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
32	0	0	32	100	7m35.938829s

Passed Tests

Name	⏱️ Duration	Suite
Get Container Logs	6.661 s	Container-Logs
Get Container Logs with only last N lines	0.524 s	Container-Logs
Remove Container	7.675 s	Container-Remove
Remove Container Non Existent Container Should Not Through An Error	0.068 s	Container-Remove
Restart Container	0.471 s	Container-Restart
Restart Unknown Container Fails	0.098 s	Container-Restart
Update to tedge-container-plugin-ng	25.513 s	Installation
Check for Update	7.858 s	Operations-Clone
Clone Existing Container	27.681 s	Operations-Clone
Clone Existing Container by Timeout Whilst Waiting For Exit	18.051 s	Operations-Clone
Clone Existing Container but Waiting For Exit	23.687 s	Operations-Clone
Ignore Containers With Given Label	21.093 s	Operations-Clone
Install/uninstall container package from private repository - credentials file	14.599 s	Operations-Private-Registries
Install/uninstall container package from private repository - credentials script	17.191 s	Operations-Private-Registries
Install/uninstall container package from private repository - credentials script with cache	22.788 s	Operations-Private-Registries
Install/uninstall container package from private repository - engine credentials	20.001 s	Operations-Private-Registries
Install/uninstall container package from private repository - docker from docker	39.553 s	Operations-Private-Registries
Get Configuration	5.442 s	Operations
Install/uninstall container-group package	16.137 s	Operations
Install invalid container-group	3.092 s	Operations
Install container-group with multiple files - app1	14.989 s	Operations
Install container-group with multiple files - app2	10.242 s	Operations
Install/uninstall container package	15.190 s	Operations
Install/uninstall container package from file	8.276 s	Operations
Manual container creation/deletion	19.963 s	Operations
Manual container creation/deletion with error on run	7.768 s	Operations
Manual container created and then killed	10.302 s	Operations
Self Update Is Present Using Self Type	0.152 s	Self
Self Update Is Present Using Container Type	0.158 s	Self
Self Update Is Not Present	0.148 s	Self
Service status	19.306 s	Telemetry-Main
Sends measurements	71.260 s	Telemetry-Main