Update git submodules

* Update docs/submodules/container4nfv from branch 'master'
  - update to vagrant 2.0.2

    vagrant 1.8 cannot download vagrant box

    Change-Id: I07252a7e5dc11f084419a44dffc1262e981f2b74
    Signed-off-by: Guo Ruijing <ruijing.guo@intel.com>

diff --git a/docs/submodules/container4nfv b/docs/submodules/container4nfv
index 073d9b6..2a777bc 160000 (submodule)
--- a/docs/submodules/container4nfv
+++ b/docs/submodules/container4nfv
@@ -1 +1 @@
-Subproject commit 073d9b661faa951055db48c27999454202f90b4f
+Subproject commit 2a777bcb738cdc247a52f43128218a67efebb5e1