Make unselected resources more robust by using section instead of conditional

[mvdbeek]

This came up during the admin training in https://training.galaxyproject.org/training-material/topics/admin/tutorials/connect-to-compute-cluster/tutorial.html#a-dynamic-destination

If a user doesn't select the job resource in the UI it needs to be handled in the python function.
If instead we changed

galaxy/lib/galaxy/jobs/__init__.py

Line 267 in ead6bb4

JOB_RESOURCE_CONDITIONAL_XML = """<conditional name="__job_resource">

to be a section the default would just be used.