Comment 8 for bug 1691274

Reviewed: https://review.openstack.org/515421
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=1d614443a7198642ef14467ab470ce1aa41f36b9
Submitter: Zuul
Branch: stable/ocata

commit 1d614443a7198642ef14467ab470ce1aa41f36b9
Author: Hongbin Lu <email address hidden>
Date: Tue May 16 20:54:25 2017 +0000

    Handle exception on adding secgroup

    If user adds security group to an instance and the instance already
    has that security group, neutron will return a 400 response. Nova
    should handle the 400 response properly. In before, Nova doesn't
    seem to handle this case and end-user gets a 500 response. This
    commit fixed it.

    Conflicts:
          nova/network/security_group/neutron_driver.py

    NOTE(hongbin): The conflict is due to the removal of translation of
    log messages.

    Closes-Bug: #1691274
    Change-Id: I58b19ef6b537d690df90e542b6af3c64773ecc87
    (cherry picked from commit 083bc89f99e007c400b9f89c63ac0459da910df8)