compute rpcapi 2.29 is not backwards compatible

[Joe Gordon]

patch 6fcf4133b49cfefa77151937dec4db097a85c349 (https://review.openstack.org/#/c/30192/) which added compute rpcapi version 2.29 does not provide any backwards compatibility, this should be done using 'self.can_send_version'

The result of this is, if compute is running grizzly and trunk is running with

[upgrade_levels]
compute=grizzly

in nova.conf

stop_instances does not work

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/43821

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/43821
Committed: http://github.com/openstack/nova/commit/1c307e592c20a53e8930e2999e885b59658e359e
Submitter: Jenkins
Branch: master

commit 1c307e592c20a53e8930e2999e885b59658e359e
Author: Jay Lau <email address hidden>
Date: Tue Aug 27 12:17:12 2013 +0800

    compute rpcapi 2.29 is not backwards compatible

    patch 6fcf4133b49cfefa77151937dec4db097a85c349 which added compute
    rpcapi version 2.29 does not provide any backwards compatibility.

    Fix this issue with 'self.can_send_version'

    Fix bug 1217068

    Change-Id: Idc49040b712058aab8d3ed769bdf18bdc0a4f067