Update git submodules

* Update docs/submodules/ipv6 from branch 'stable/euphrates'
  - Updated User Guide

    Change-Id: Ieb62a40e34638aaffd6dc8b25493047142e5dbe7
    Signed-off-by: Bin Hu <bh526r@att.com>
    (cherry picked from commit be8ef89c7d887117aa6f0d6ef3086509b0dbb3b3)

diff --git a/docs/submodules/ipv6 b/docs/submodules/ipv6
index f5a86b0..f9aeee1 160000 (submodule)
--- a/docs/submodules/ipv6
+++ b/docs/submodules/ipv6
@@ -1 +1 @@
-Subproject commit f5a86b0d99594c659cb35ba98b0c423fe82c06c7
+Subproject commit f9aeee14fd64491eaae522c16e87ba015da0eb9a