Comment 4 for bug 1795129

Reviewed: https://review.openstack.org/616992
Committed: https://git.openstack.org/cgit/openstack/os-net-config/commit/?id=6252d770baa55ca3ab28be8cfd0d5ea50f32bed0
Submitter: Zuul
Branch: stable/rocky

commit 6252d770baa55ca3ab28be8cfd0d5ea50f32bed0
Author: Dan Sneddon <email address hidden>
Date: Sat Sep 29 04:28:14 2018 -0700

    Apply IP/netmask/route/MTU changes without bouncing interfaces.

    Modifications to impl_ifcfg.py to support making changes to IP
    address, MTU, and routes live, rather than running ifdown/ifup on the
    interface. Bouncing the interface is very disruptive, especially with
    bridges where all the child interfaces are also bounced.

    If only the IP address, netmask, MTU, routes, and/or boot status are
    changed, the file will be written and 'ip' or 'ip route' commands
    will be run to apply the new config on the fly. If any commands fail,
    the interface will be restarted instead.

    Closes-bug: 1795129
    Change-Id: I75239fd3f273a88feb80f09a67aa5a947d64ac30
    (cherry picked from commit c9bf347a238d45072c54d0915e4b9ea0a8683a17)