This patch updates the install instruction of Tacker in Devstack
with two modes, i.e., all-in-one mode and standalone mode.
It also removes some redundant configurations in local.conf.example
which already had in the Devstack settings.
Change-Id: I6d8d1bbe54b1a382fcbf83a1aef1fa389c43c1fc
4cddc815c2