Update git submodules

* Update docs/submodules/apex from branch 'stable/euphrates'
  - nosdn-fdio scenarios fixes

    - pin vpp/networking-vpp versions
    - Add external_network_bridge config back to puppet-neutron

    Change-Id: Ia58fb55638390757ea3350b2921897c4d315f9b5
    Signed-off-by: Feng Pan <fpan@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 2be3a2c..2ee71b2 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 2be3a2ce5c1c90c489f424bc9ac80de5336bbcc5
+Subproject commit 2ee71b201c0a607f1814bf5fe3e6971f6357db42