Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Add core pinning settings for VPP"
  - Add core pinning settings for VPP

    Also updated os-net-config to enable VPP service on startup,
    as well as updating show interfaces command.

    JIRA: APEX-407
    os-net-config-pr: 6
    opnfv-tht-pr: 129

    Change-Id: I77c590e966d2532d894ec96bb60ffdf914a90f6d
    Signed-off-by: Feng Pan <fpan@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 2a1c559..2852914 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 2a1c5597cf4f3c018b5064fded8cdb5637f98e68
+Subproject commit 28529146f87e5b725616c6574e69697410975f77