Correct typo in install role README
Correct typo in install role README

Change-Id: I7c4e073e4f8defb394164948cdee850f9f721dd7

openstack/bifrost,bcornec/bifrost,devananda/bifrost,EntropyWorks/bifrost,bcornec/bifrost,devananda/bifrost,openstack/bifrost,EntropyWorks/bifrost