Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Fix deployment errors for odl-fdio scenarios"
  - Fix deployment errors for odl-fdio scenarios

    - Changed NIC template generation to only configure VPP interface for
      external network on compute nodes
    - Fixed overcloud deploy environment file error when deploying odl-fdio

    Change-Id: I4fb07073b0dffc35ef09a5e32deb8470f5ee8347
    Signed-off-by: Feng Pan <fpan@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 5398acb..c81b847 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 5398acb7f2fa497e0666912b97b6e41cf87d3d14
+Subproject commit c81b847004aeed37931ee2e8ba53ebc193598fd0