in init_l3 ip address delete may occurrent delete multiple ips

[Zang MingJie]

For example:

# ip ad add 10.1.1.1/24 dev lo
# ip ad add 10.1.1.2/24 dev lo

# ip ad
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 10.1.1.1/24 scope global lo
       valid_lft forever preferred_lft forever
    inet 10.1.1.2/24 scope global secondary lo
       valid_lft forever preferred_lft forever

# ip ad del 10.1.1.1/24 dev lo
# ip ad
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

Added two ips, and deleted one, all ips are gone.

This is because 10.1.1.2 is secondary, if the primary address is deleted, also does the secondary address.

There is an sysconf entry controls the behaviour of deleting primary ip (/proc/sys/net/ipv4/conf/all/promote_secondaries). when set instead of deleting the secondary address, it will be promoted to primary ip

We should set it when creating a namespace.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/107743

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/107743
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=141a00bd274ea7f90fcfe784e358bb6035af6e84
Submitter: Jenkins
Branch: master

commit 141a00bd274ea7f90fcfe784e358bb6035af6e84
Author: Zang MingJie <email address hidden>
Date: Thu Jul 17 23:06:07 2014 +0800

    Set promote_secondaries when creating namespaces

    there is a sysconf entry which controls how deletion of the primary ip
    is performed (/proc/sys/net/ipv4/conf/all/promote_secondaries). when set
    instead of deleting the secondary addresses, one of them will be
    promoted to primary ip.

    Without it, when init_l3 called on a port, it may unexpectedly delete
    some useful ips.

    Change-Id: I0b1b3bd6ade21129532c842daa31059ea164719e
    Closes-bug: 1343320