Make SFC test a python call to main()

Make SFC test a python call to main()

Instead of python -> bash -> python, call
the SFC test using the execute() method that
is inherited from FeatureBase and it's a bash
call by default.
With this change, we call the SFC test using main()
of run_tests.py of SFC repo and will have
real time output.

Change-Id: I6d59821e603c88697a82b95c5626c5b703c11026
Signed-off-by: jose.lausuch <jose.lausuch@ericsson.com>
Signed-off-by: George Paraskevopoulos <geopar@intracom-telecom.com>
(cherry picked from commit d5820bef80ea4bdb871380dbfe41db12290fc5f8)