Update git submodules

* Update docs/submodules/container4nfv from branch 'stable/euphrates'
  - E release note

    Change-Id: I1b5ecaf5e79df6800fdf44be797dbdbee75631a7
    Signed-off-by: Xuan Jia <jason.jiaxuan@gmail.com>
    (cherry picked from commit e5476e92b95b4cca079381ceac7e3a7b147c38a2)

diff --git a/docs/submodules/container4nfv b/docs/submodules/container4nfv
index f874546..644f51f 160000 (submodule)
--- a/docs/submodules/container4nfv
+++ b/docs/submodules/container4nfv
@@ -1 +1 @@
-Subproject commit f8745467295773dd0eea75079f5e2b0b50bfcd2e
+Subproject commit 644f51f420a38b494a2c6af60ac5a8134c733931