build: install python-dbusmock via pip for a Docker container

[alexeykuzmin]

Description of Change

To prevent timeout errors with some other python-dbusmock versions.

Related to #18523.

• Linux builds are timing out but passing tests. It turns out that dbusmock was hanging on dbus_stop. This PR changes the docker container to use a newer version of python-dbusmock which adds timeouts to dbus_stop.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• PR title follows semantic commit guidelines

Release Notes

Notes: no-notes

[codebytere]

@alexeykuzmin what timeout errors were we seeing? do you have links to relevant tests that were dying, by chance?

[alexeykuzmin]

@codebytere see the second bullet point in the #18523 linked in the description.

[alexeykuzmin]

@jkleinsc I remember you saying that all containers for branches > 3 work fine,
but if we'll have to build a new container version, it will get python-dbusmock 0.17.0-1 with which I see that timeout issue.

[jkleinsc]

@alexeykuzmin the change I was picking up for 3-1-x was the change to actually have a timeout on dbus_stop, which you can see was added in 0.17: https://github.com/martinpitt/python-dbusmock/blob/master/NEWS#L31

We still see the timeout message, but it works better than before where it would wait forever. That I can tell the timeout issue is still in 0.18.2 so I would recommend just changing the Docker file to pull in the latest so that once a new version is released if would pick up this commit:
martinpitt/python-dbusmock@f3b9d61

[release-clerk]

No Release Notes

[trop]

I have automatically backported this PR to "6-0-x", please check out #18597

[trop]

I have automatically backported this PR to "4-2-x", please check out #18598

[trop]

I have automatically backported this PR to "5-0-x", please check out #18599