Set defaultbranch in .gitreview to stable/essex
Set defaultbranch in .gitreview to stable/essex

This allows people run git-review without any arguments.

Change-Id: I3f1c7ce22cbe40ed34f084fd3dbc0941ba787bcf

cbrucks/keystone_ldap,cbrucks/keystone_ldap,cbrucks/keystone_ldap