Update git submodules

* Update docs/submodules/sfc from branch 'stable/danube'
  - Fix checking for optional cmd line args in cleanup

    Change-Id: I5305e7c6426e0a563499f0aeefd910ce03e5ceae
    Signed-off-by: George Paraskevopoulos <geopar@intracom-telecom.com>
    (cherry picked from commit 6d6d321145befb9f823a9d8af40e5dce83f0dbc7)

diff --git a/docs/submodules/sfc b/docs/submodules/sfc
index 979951f..54ac611 160000 (submodule)
--- a/docs/submodules/sfc
+++ b/docs/submodules/sfc
@@ -1 +1 @@
-Subproject commit 979951f484dbb1126356d03abf13f93082f2646b
+Subproject commit 54ac61161108b037c1ccb3dca9cd2640f46b78b9