fix typo in config.py
fix typo in config.py

Change help text from GigaByte to Gigabyte.

Change-Id: Ic8e1f4472812aa501ffa0588b782f9fce5832af4
Signed-off-by: Danny Al-Gaaf <473e39ac77cf392f0dd9bacde8409de76c14d006@bisect.de>

sajuptpm/manila,jcsp/manila,redhat-openstack/manila,bswartz/manila,NetApp/manila,jcsp/manila,scality/manila,bswartz/manila,vponomaryov/manila,openstack/manila,redhat-openstack/manila,weiting-chen/manila,NetApp/manila,openstack/manila,sajuptpm/manila,scality/manila,vponomaryov/manila,weiting-chen/manila