moving ips fails intermitently because the ip exists.

[Vish Ishaya]

The ip addr add and delete command sometimes fails because the ip is already on the device. We should check for this failure and continue as if the ip was added.

The same is true for the route commands.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/3000

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/3000
Committed: http://github.com/openstack/nova/commit/e40ee23abab92f863f53f6ba4041e3e04cf2a89f
Submitter: Jenkins
Branch: master

commit e40ee23abab92f863f53f6ba4041e3e04cf2a89f
Author: Vishvananda Ishaya <email address hidden>
Date: Thu Jan 12 11:13:42 2012 -0800

    Updates linux_net to ignore some shell errors

     * Allows exit 254 from ip add and ip del
     * Allows exit 7 from route add and route del
     * These exit codes means the ip/route already existed or was
       already removed
     * Fixes bug 915556

    Change-Id: Ib71da2351372f3c7e3558cf5b3e9f55e10681875