Add retry on upload_vhd in xapi glance plugin

[Nicholas Kuechler]

Add a retry in the xapi glance plugin to handle transient issues when uploading the vhd.

An example issue we're seeing is a connection timeout:

['XENAPI_PLUGIN_FAILURE', 'upload_vhd', 'error', "(110, 'Connection timed out')"]

To work around transient issues such as a connection timeout, I think the glance plugin should retry the upload a small number of times before outright failing.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/23093

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/23093
Committed: http://github.com/openstack/nova/commit/2db1a0f62b797acdb8506e7e36fbced0828dd796
Submitter: Jenkins
Branch: master

commit 2db1a0f62b797acdb8506e7e36fbced0828dd796
Author: Nicholas Kuechler <email address hidden>
Date: Wed Feb 27 10:02:33 2013 -0600

    Adds retry on upload_vhd for xapi glance plugin

    Add a retry for the xapi glance plugin to handle transient issues
    when uploading the vhd.

    An example issue we're seeing is a connection timeout:

    ['XENAPI_PLUGIN_FAILURE', 'upload_vhd', 'error',
      "(110, 'Connection timed out')"]

    To work around transient issues such as a connection timeout, we
    should retry based on glance_num_retries before outright failing.

    Change-Id: Ice6fdd3dd39ef40e5997d69209aaafa66bff5d6e
    Fixes: bug #1134493