Drop support for conductor 1.x rpc interface

In commit 330ce897c14f66a39426e716f02a620453035c15, a part of
Icehouse, we added support for the 2.x interface.  Now that Juno
development is open, we can drop support for the old API, 1.x.

For more information on this change, see:

    https://wiki.openstack.org/wiki/RpcMajorVersionUpdates

UpgradeImpact

Change-Id: Id7e605d493a53eaaa2a9afa0c99ac721f590ca3f
Merge "Drop support for conductor 1.x rpc interface"