Bug 1396 : Change from deprecated DataBrokerService to DataBroker

Bug 1396 : Change from deprecated DataBrokerService to DataBroker

As a follow up from my conversation with edwarnicke, it turns out that
OVSDB should be in charge of creating whatever missing parents it needs
for the flow creation configuration. An issue still remains in regards
to who/when removes the node portion of the tree once all flows are
removed. That will be tracked by another bug, and bug 1396 will be
linked with it.

For more details, see: https://gist.github.com/864043e0a96c4e704497

Change-Id: I0f28a369c55e7af3d84fc7ddbef93f0efe3f5b30
Signed-off-by: Flavio Fernandes <ffernand@redhat.com>