Topology: Remove dispach by method name construction

[Dima Kuznetsov]

Topology looks for port event handler by:
1. extracting type of the port
2. creating handler name '_{type}_{action}'
3. checking if method exists.

Since there are not that many options, its nicer to dispatch them directly.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/519322
Committed: https://git.openstack.org/cgit/openstack/dragonflow/commit/?id=adadf17948c5a44433e58d22f7f770d233f89a96
Submitter: Zuul
Branch: master

commit adadf17948c5a44433e58d22f7f770d233f89a96
Author: Dima Kuznetsov <email address hidden>
Date: Mon Nov 13 10:05:04 2017 +0200

    Topology: move filtering to ovsdb monitor

    Topology app keeps a local ovs port cache because it does not want all
    port updates to take effect. In particular, events with missing data
    (ofport, type). Moving this logic to vswitch_impl because it makes a lot
    of sense to hold off those events even for apps that consume OvsPorts.

    Partial-Bug: #1737339
    Change-Id: I0bc8053d6fb3ed277028cf6bce9c6a0269e601af

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/519323
Committed: https://git.openstack.org/cgit/openstack/dragonflow/commit/?id=2de5a5f64ac18f46ba2cd0e93eaeb61bdaf0e473
Submitter: Zuul
Branch: master

commit 2de5a5f64ac18f46ba2cd0e93eaeb61bdaf0e473
Author: Dima Kuznetsov <email address hidden>
Date: Mon Nov 13 10:20:02 2017 +0200

    Topology: remove local cache of OVS ports

    A previous patch moves all OvsPort filtering to vswitch_impl. This makes
    all updates valid for topology. This patch removes the local cache in
    favor of using DbStore.

    Partial-Bug: #1737339
    Change-Id: I686ec4dc99eda643db85b2a4f706250e58155e89

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/519324
Committed: https://git.openstack.org/cgit/openstack/dragonflow/commit/?id=f593475a6a03a2e9a1b00710a1485cc0550f58cd
Submitter: Zuul
Branch: master

commit f593475a6a03a2e9a1b00710a1485cc0550f58cd
Author: Dima Kuznetsov <email address hidden>
Date: Mon Nov 13 09:03:31 2017 +0200

    Topology: dispatch ovs port events directly

    This changes discards dynamic handler retrieval in favor of direct
    method calls. Old code was doing something along the lines of:

     handler = getattr(self, '_{port_type}_{action}')
     if handler:
         # ....

    Since there aren't that much cases to cover, and the dynamic resolution
    makes it a bit hard to navigate around the code, this patch removes it
    in favor of direct approach.

    Closes-Bug: #1737339
    Change-Id: Icbe50c0c74bcfaa89903e18808c3beca616638f8