Per container flow statistics filtering to account cFlows

Per container flow statistics filtering to account cFlows

ISSUE:
ReadServiceFilter in openflow protocol plugin while trying to derive
to which container a flow statistics object belongs, it does not take into
account the container flows (cFlows).
CHANGES:
- Have ReadServiceFilter maintain a map of container to container flows
- Have flowBelongToContainer() account the cFlows while filtering the Flow objects
- Changed the other container maps to concurrent maps
- Other minor style changes

Change-Id: I2d41fa2111334d57ef3179e907fea0bf268943e7
Signed-off-by: Alessandro Boch <aboch@cisco.com>