Make it possible to pass OVN_SRCDIR to tox so that compiling isn't
necessary if you already have a functional OVN_SRCDIR, e.g. if
deploying with devstack with OVN_BUILD_FROM_SOURCE=True
Change-Id: If966de7dec93ba71f05d48e1d58d3369ce5f4e0a
Signed-off-by: Terry Wilson <twilson@redhat.com>
f4ddd3ae9b