List system dependencies for running common tests

Add an other-requirements.txt file containing a cross-platform list
of dependencies needed for running included tox-based tests. Also
include a tox environment for convenience calling the bindep[*]
utility to list any missing system requirements.

This change is self-testing.

For other-requirements.txt see also
http://docs.openstack.org/infra/manual/drivers.html#package-requirements

[*] http://docs.openstack.org/infra/bindep/

Change-Id: I3c62f6924d2d70e23e6787b8da848fbeb0d52ddc
(cherry picked from commit d6ca9e2d7473f6d15a3c76bcd5a7c3cc65b49296)
2 files changed