teuthology/Dockerfile: add env setuptools-scm version

teuthology/Dockerfile: add env setuptools-scm version

Because the teuthology code is building in container after
copying source code from local directory, but no corresponding
git repo copied, the setuptools-scm cannot determine teuthology
version. So in order to produce the package we just provide dummy
version 0.0.0 using environment variable:

  SETUPTOOLS_SCM_PRETEND_VERSION_FOR_TEUTHOLOGY

Signed-off-by: Kyr Shatskyy <kyrylo.shatskyy@clyso.com>