Set Tempest storage protocol and vendor w/o setting driver

Set TEMPEST_STORAGE_PROTOCOL and TEMPEST_VOLUME_VENDOR if
they are changed from their defaults, or if
TEMPEST_VOLUME_DRIVER is changed.

This maintains the current behavior of setting these options if
TEMPEST_VOLUME_DRIVER is set to something other than "default".

Change-Id: I1fb7f5db0446f97de48b97a6f451882cc51c51a4
Reference git.o.o DevStack repo rather than GitHub

In docs, use git.o.o URLs rather than GitHub URLs for the DevStack repo,
and don't mention GitHub when git.o.o is more appropriate.
Also, replaced GitHub logo with Git logo in quickstart.png.

Change-Id: Iab0006144f008963b8cb5be2d10ce0f360c0e6ca
Remove internal bash8

We use the one installed from pypi in the tox venv, so dump
the original.  Fix up run_tests.sh.

Change-Id: I6b0aa1da9bfa4d742a7210e6ff800d72492a2178
Merge "Reference git.o.o DevStack repo rather than GitHub"
Merge "Set Tempest storage protocol and vendor w/o setting driver"
Merge "Remove internal bash8"
Merge branch 'master' of https://github.com/openstack-dev/devstack