Changed sff_rest.py to sfc_agent.py

sff_rest is not a SFF anymore. It has become a SFC agent that creates
SFF, SF and others based on ODL messages.

Change-Id: I30c3465095d6ac332b87ce8cdfbe643a804e7f34
Signed-off-by: Reinaldo Penno <rapenno@gmail.com>