BSN: Set hash header to empty instead of False

Sets the consistency hash header to empty instead
of False since 'False' is handled like a string on
the backend and requires special-casing to detect.

Conflicts:

	neutron/tests/unit/bigswitch/test_servermanager.py

Change-Id: Iee1651574c01a32e78167a9bbed4e0433abbdec2
Closes-Bug: #1325771
(cherry-picked from 7b9ed4edeef7d599c164c8682fbbb36066d98abb)
Merge "BSN: Set hash header to empty instead of False" into stable/icehouse