Fix typo of 'authenticaiton'
Fix typo of 'authenticaiton'

This patch corrects word 'authenticaiton' to 'authentication' in
ironic/dhcp/base.py

Change-Id: I4667a8d12539bd2f45a5f73bfc534068158a2e8f

SauloAislan/ironic,openstack/ironic,NaohiroTamura/ironic,NaohiroTamura/ironic,pshchelo/ironic,openstack/ironic,pshchelo/ironic,SauloAislan/ironic