Update git submodules

* Update docs/submodules/sfc from branch 'master'
  - Create unit tests for 'cleanup.py' module

    This is the first attempt to add unit testing capabilities
    to OPNFV/SFC project.

    Also we are following the contraints.txt logic which
    helps in the direction of simulating a test env which
    will be as much as close to the real env that the SFC
    testcases are running.

    Jira: SFC-127
    Jira: SFC-129

    Change-Id: I938d28f9f85614cdefa163949c4ec9f06f5d27b4
    Signed-off-by: Dimitrios Markou <mardim@intracom-telecom.com>

diff --git a/docs/submodules/sfc b/docs/submodules/sfc
index f09fb2d..ee231b9 160000 (submodule)
--- a/docs/submodules/sfc
+++ b/docs/submodules/sfc
@@ -1 +1 @@
-Subproject commit f09fb2d100e06d72568dd039f1cf83dc2c6f5847
+Subproject commit ee231b97dbb139ae31d9967b8f3a8ac9611256b0