Dynamic Jobs force "docker-image" Jobs Context to Output Folder

[calvinmorrow]

Describe the bug
Dynamic jobs created via an output to /infrabox/output/infrabox.json force future docker-image jobs to lose Git context by binding /infrabox/context to /data/repo/.infrabox/output

To Reproduce

1. Create a dynamic job by copying an infrabox.json file to /infrabox/output/infrabox.json with a docker-image type job.
2. Git repo is cloned like normal
3. Git context is inaccessible because docker mounts are as follows:

        "Mounts": [
            {
                "Type": "bind",
                "Source": "/data/repo/.infrabox",
                "Destination": "/infrabox",
                "Mode": "",
                "RW": true,
                "Propagation": "rprivate"
            },
            {
                "Type": "bind",
                "Source": "/data/repo/.infrabox/output",
                "Destination": "/infrabox/context",
                "Mode": "",
                "RW": true,
                "Propagation": "rprivate"
            }
        ],

Expected behavior
Normal docker-image jobs would have context set to the git repo (/data/repo). Context is empty unless other files are copied to /infrabox/output

I am assuming this is unintended behavior. At the least it seems undocumented behavior. Context is set in job.py to the Infrabox output folder in https://github.com/SAP/InfraBox/blob/master/src/job/job.py#L445-L454.

Our use case was to write a tool that would run workflows (specific infrabox.json files) on specific branches. If the branch matched, the file was copied to /infrabox/output/infrabox.json (ie: master or release branch workflows). Unfortunately the workflows subsequently failed because the git repo was inaccessible to the dynamically created jobs.

Clarifying that this issue primarily affects docker-image jobs since in docker jobs the build_context can be changed (to ../.. in most examples I've seen) which I don't believe is possible with docker-image