Fixes configplugin execution bug

If we get an AttributeError, when executing yaml.load(), the execution of the
plugin fails. This patch fixes this issue.

Change-Id: Icc5d46adaf4e63e00e6e346161b7cccf93d2e4dd
Remove deprecated static network config method

Refactor all the services in such way that they support
the new `get_network_details` method instead of the old
`get_network_config` method for statically configuring
network interfaces through the networkconfig plugin.

Change-Id: Idb519935da0d3aee316ad9bc9451f74bc80b12ba