Fix relative import path in source tree

This patch fixes the relative import path to use congress
as the base to be consistant with other openstack projects. In addition,
this commit removes the the run_congress_server script and replaces that
with bin/congress-server and the run_test script.

Unit tests can now be successfully be run by issuing:
make
tox -epy27 (once the tox.ini enables tests again).

Closes-bug: 1338840

Change-Id: I371192e9573a7f1ca4ea8e1d6a707e265e8f8dc9
Merge "Fix relative import path in source tree"