Update git submodules

* Update docs/submodules/sfc from branch 'master'
  - Harmonize vxlan-tool calls

    Renamed vxlan_firewall and vxlan_tool_stop to start_vxlan_tool and
    stop_vxlan_tool respectively. Added some comments to explain their
    behavior.

    Cleaned both functions to use ".format()" string formatting, which
    improves readability.

    Modified behavior of start_vxlan_tool: now it does NOT block
    traffic by default

    Change-Id: I6754b020a474be1e9adf2d83e7c9f5053930b702
    Signed-off-by: Juan Vidal <juan.vidal.allende@ericsson.com>

diff --git a/docs/submodules/sfc b/docs/submodules/sfc
index 6d6d321..8a66eac 160000 (submodule)
--- a/docs/submodules/sfc
+++ b/docs/submodules/sfc
@@ -1 +1 @@
-Subproject commit 6d6d321145befb9f823a9d8af40e5dce83f0dbc7
+Subproject commit 8a66eac4bbb898d943d461845e371381425a9cf7