fix running --containerize --container-build-image with --extended-dry-run

[boegel]

singularity --version always need to be run, to avoid this crash:

Traceback (most recent call last):
  File "/example/easybuild-framework/test/framework/containers.py", line 260, in test_end2end_singularity_image
    stdout, stderr = self.run_main(args)
  File "/example/easybuild-framework/test/framework/containers.py", line 84, in run_main
    self.eb_main(args, raise_error=True, verbose=True, do_build=True)
  File "/example/easybuild-framework/test/framework/utilities.py", line 295, in eb_main
    raise myerr
AttributeError: LooseVersion instance has no attribute 'version'

cc @shahzebsiddiqui

[boegel]

@FooBarQuaxx you'll need to sync your branch for #2479 with develop after this gets merged, and resolve the merge conflicts

[ocaisa]

Lgtm