Support sending 'If-Match' constraints in Header

[hongbin]

Neutron server supports 'If-Match' constraints [1] but neutronclient doesn't seem to support it yet.

[1] https://developer.openstack.org/api-ref/network/v2/#revisions

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/526981

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/526984

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/526981
Committed: https://git.openstack.org/cgit/openstack/python-neutronclient/commit/?id=cefa2432f677b8812330950055f285b13790080a
Submitter: Zuul
Branch: master

commit cefa2432f677b8812330950055f285b13790080a
Author: Hongbin Lu <email address hidden>
Date: Mon Dec 11 05:26:39 2017 +0000

    Pass headers to httpclient

    Right now, it is impossible to set HTTP headers in client because
    the 'headers' parameter is not set. This patch fixes it.

    Change-Id: Iff002aaca516e8d014074f120b7f713758ebf265
    Partial-Bug: #1737473

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/526984
Committed: https://git.openstack.org/cgit/openstack/python-neutronclient/commit/?id=c02b8074aa5767d527b48c2c3aeffde57ca2d8fb
Submitter: Zuul
Branch: master

commit c02b8074aa5767d527b48c2c3aeffde57ca2d8fb
Author: Hongbin Lu <email address hidden>
Date: Mon Dec 11 05:55:14 2017 +0000

    Add 'revision_number' to update_* API

    This allows API consumers to leverage the If-Match HTTP header to
    conditionally update a resource

    Change-Id: Iaa98ce0436dad3d93cd295090f660c729899a0c8
    Partial-Bug: #1737473
    Related-Bug: #1417975