Update git submodules

* Update docs/submodules/apex from branch 'stable/fraser'
  - Enable nosdn-fdio scenarios for Fraser release

    - Update neutron NSDriver patch
    - Update os-net-config to fix config errors for vpp uio-driver
    - Update puppet-tripleo to add configuration of physnets and type_driver
      in vpp agent
    - Update THT to change VPP environment file for vpp-agent, and add common.yaml
      for vpp interface mapping
    - Update VPP and networking-vpp version to 18.01
    - Fix networking-vpp rpm build to enable proper uninstall.
    - Update networking settings file to use ovs_bridge as default external interface type

    JIRA: APEX-578
    JIRA: APEX-568
    JIRA: APEX-576
    JIRA: APEX-577

    apex-os-net-config: I915d5455acb8d496438b9c9e851639d3a43e6fa9
    apex-puppet-tripleo: I472879b8f67e64b571638a0385943597a9120e6c
    apex-tripleo-heat-templates: I5dfaf85d67fb038109edaf5c5d8a3e901b9148f4

    Change-Id: I369bee232bfafef260d2ef19ac32614fdc487271
    Signed-off-by: Feng Pan <fpan@redhat.com>
    (cherry picked from commit 0cd3c6cef32adb1bf9d26414ed73bd9373b0c407)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 814c37e..4b8f1b1 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 814c37ee17c9e797b5a4f1944bd52facf22fb513
+Subproject commit 4b8f1b163570256eee7cf69f4de61c7c6a84046c