Add ex_get_network to openstack driver

[SanderRoosingh]

Description

Currently to retrieve a network from the OpenStack all networks need to be received. Then these can be filtered by ID. If the ID of the network is known it is not needed to retrieve all networks from the OpenStack.

By creating a function called ex_get_network and passing an ID we could retrieve a single network, this would increase performance for some systems. This function works similar to ex_get_volume.

fixes #1473

Status

• done, ready for review

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks)
• Documentation
• Tests
• ICLA (required for bigger changes)

[vdloo]

Tested both the v1 and v2 driver, both work fine:

The OpenStack_1_1_NodeDriver:

In [12]: conn.__class__.__bases__
Out[12]: (libcloud.compute.drivers.openstack.OpenStack_1_1_NodeDriver,)

In [13]: network_id = conn.ex_list_networks()[0].id

In [14]: conn.ex_get_network(network_id)
Out[14]: <OpenStackNetwork id="123c6b6a-1234-3a1f-b404-1234365f4b22" name="L2_NETWORK" cidr="None">

The OpenStack_2_NodeDriver:

In [3]: conn.__class__.__bases__
Out[3]: (libcloud.compute.drivers.openstack.OpenStack_2_NodeDriver,)

In [4]: network_id = conn.ex_list_networks()[0].id

In [5]: conn.ex_get_network(network_id)
Out[5]: <OpenStackNetwork id="123c6b6a-1234-3a1f-b404-1234365f4b22" name="L2_NETWORK" cidr="None">

The failing tests (scrape-and-publish-provider-prices) are unrelated.

lgtm 👍

[Kami]

LGTM, thanks for the contribution and thanks to @vdloo for testing the changes.

I pushed 9807ded which should fix the failing Travis CI job.