Add rollback for Cisco plugin update_port failure

Fixes bug 1174433

This fix adds a rollback of the OVS plugin update_port operation
following a failure to update the port in the Cisco Nexus sub-plugin.

Also, this fix removes an unneccessary call to the Nexus sub-plugin's
update_network method within the Cisco plugin model layer's
update_network method (as well as the associated argument setup).
The Nexus sub-plugin's update_network is a no-op, so there's no
need to call it.

Change-Id: I10cba0d7f1d632c7f77eb6c4a94ea82b958bc6a2
Rename README to README.rst

README.rst seems to be more standard accross OpenStack
modules. Also add it to the manifest. Fix a typo
in the manifest.

Fixes: LP Bug #1186518

Change-Id: Ib04f44a1186d3793f5fca39c0c29d74a78a52faf
Port profile should not mark vlan as native-vlan

Change-Id: I0b117ad8a3761e8f8ae59ae21fb68bbc3303b35b
Fixes: bug 1186461
Merge "Add rollback for Cisco plugin update_port failure"
Merge "Port profile should not mark vlan as native-vlan"
Merge "Rename README to README.rst"