Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Merge "Add overlay_ip_version config for IPv6 tenant networks" into stable/danube
  - Add overlay_ip_version config for IPv6 tenant networks

    JIRA: APEX-443
    opnfv-tht-pr: 133

    Change-Id: I03b28bdcc6d0649920fd58fb3400b2a4e5891e68
    Signed-off-by: Feng Pan <fpan@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 652d97b..341d03f 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 652d97b4808ae3cd31a7440d59bc50cb0a157143
+Subproject commit 341d03f86b718e0d556c2e12baebdca8760a28ec