add two times of flow entries for active port

[hujie]

When restart dragonflow controller, it will pull data from df db, and lport event will come earlier than active port event, in _notify_active_ports_updated_when_lport_created method in lport process, it will fetch the active port data from df db and try to add flow entry for the lport, and when come to the update_activeport method in active port process, it will fetch the lport again and add the same flow entry again, it is unnecessary.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/435700

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/435700
Committed: https://git.openstack.org/cgit/openstack/dragonflow/commit/?id=b2bde3f591b3939bd3d0ad54e1cba481c7d21e07
Submitter: Jenkins
Branch: master

commit b2bde3f591b3939bd3d0ad54e1cba481c7d21e07
Author: hujie <email address hidden>
Date: Sat Feb 18 20:12:28 2017 +0800

    Fix add flow twice bug for active port

    when df restart, it will add flow twice in current code, this patch fix
    the bug by searching corresponding data from db cache instead of from
    redis when lport online, and store the active port into cache when no
    lport be found first which will wait the lport online later.

    Change-Id: I206e13cc36dce8b4be03a45cdd21c7b4d6d4d99f
    Closes-bug: #1665868