Update git submodules

* Update docs/submodules/ipv6 from branch 'master'
  - Preliminary documentation for Euphrates Release

    Change-Id: I1a61ac77a38530a00daf109c9a428d2c0ba96c51
    Signed-off-by: Bin Hu <bh526r@att.com>

diff --git a/docs/submodules/ipv6 b/docs/submodules/ipv6
index a3b2366..bdab3bc 160000 (submodule)
--- a/docs/submodules/ipv6
+++ b/docs/submodules/ipv6
@@ -1 +1 @@
-Subproject commit a3b23660532d314de57a51c98ef30dddf14f5e8f
+Subproject commit bdab3bc97aed17b937a314db465427a1a94f9a09