Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Fix barometer install failure

    We are seeing pip3 not found and collectd-write_sensu package conflicts
    with latest pike overcloud images. This patch changes pip3 install to
    python34-pip3 and updates collectd-write_sensu package version when
    removing.

    Change-Id: I7dfe1f2f39c3f21bffde8cfc6066f5bae66677d6
    Signed-off-by: Feng Pan <fpan@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 0cd3c6c..1abb8ac 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 0cd3c6cef32adb1bf9d26414ed73bd9373b0c407
+Subproject commit 1abb8ac25c48d182bc267d23f618043fbd7e0843