correct typo of config option name in error message
correct typo of config option name in error message

Change-Id: I146e6ac742649ec24c6fbfd8b73a5359e447e76f

metacloud/python-keystoneclient,ging/python-keystoneclient,jamielennox/python-keystoneclient,metacloud/python-keystoneclient,magic0704/python-keystoneclient,magic0704/python-keystoneclient,alexpilotti/python-keystoneclient,ging/python-keystoneclient,Mercador/python-keystoneclient,jamielennox/python-keystoneclient,sdpp/python-keystoneclient,alexpilotti/python-keystoneclient,Mercador/python-keystoneclient,darren-wang/ksc,sdpp/python-keystoneclient,darren-wang/ksc,klmitch/python-keystoneclient,jamielennox/python-keystoneclient,klmitch/python-keystoneclient