Make homingBB optinal and fix homing process

Make homingBB optinal and fix homing process

Properly defined whether or not to call homing at AssignVnfBB where by
default homing doesn't get called, but if a homing solution is provided,
then we resolve the solutions.
The goal is to change the BPMN definition to use serviceTask rather
than a scriptTask, allowing to use the Srping component to inject
logic.
Also we create a new HomingV2 component that is agnostic of the homing
implementation, which goal is to route the homing request to the proper
bbackend implementation; e.g. oof vs homing.
Finally, we remove the un-needed variables set in the execution context.

Change-Id: Ic9fb2a599c6375617c92a6d3462b62921ee47a6f
Issue-ID: SO-1168
Signed-off-by: Alexis de Talhouët <adetalhouet89@gmail.com>