This removes all of the ironic code from the devstack tree, in favor of
the devstack plugin in Ironic's tree.
Depends-On: I659e3de5c64df798441798ff48ba5c9c0506585a
Depends-On: I2c52bc014f1b0dbc6b0ae22a4deb4132b4c28621
Change-Id: I5125fce295c79600781469c2f48bea80e7600081