Update git submodules

* Update docs/submodules/container4nfv from branch 'master'
  - build vagrant box by chef/bento

    Change-Id: I83bfb13ae8c0dcf48c3ab23054cfe4531c12fa8e
    Signed-off-by: Guo Ruijing <ruijing.guo@intel.com>

diff --git a/docs/submodules/container4nfv b/docs/submodules/container4nfv
index d211672..39730e3 160000 (submodule)
--- a/docs/submodules/container4nfv
+++ b/docs/submodules/container4nfv
@@ -1 +1 @@
-Subproject commit d2116720abfb794375875c1b41c0bc06e2f3e7db
+Subproject commit 39730e33e9e020930990e4f9d23128df25a2c94c