call generate clientmanager once in interactive mode

[wanghong]

In interactive mode, OpenStackShell will still call prepare_to_run_command method before run command, and, in prepare_to_run_command method we will generate a clientmanager instance. So, we are repeated to generate clientmanager instance when run command.

I think, this should be avoided, we should only generate one clientmanager instance in interactive mode.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/129537

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/129537
Committed: https://git.openstack.org/cgit/openstack/python-openstackclient/commit/?id=f600c0eafbf9aff23b6efa1c7b94797a25873b99
Submitter: Jenkins
Branch: master

commit f600c0eafbf9aff23b6efa1c7b94797a25873b99
Author: wanghong <email address hidden>
Date: Mon Oct 20 15:29:53 2014 +0800

    only generate one clientmanager instance in interactive mode

    Currently, we repeated to generate clientmanager instance when run
    command in interactive mode. This should be avoided.

    Change-Id: I0536a690bc173be38af08a2e4443115532041efd
    Closes-Bug: #1383083