Update git submodules

Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Fix nosdn fdio scenario"
  - Fix nosdn fdio scenario

    - Update networking-vpp to use master branch
    - Update THT vpp ml2 environment file with correct parameters
    - Update external network creation command to use 'externa' as
      provider network name.
    - Remove vpp network settings file as it's not used

    apex-tripleo-heat-templates: Ia25db8456f1ad6beb96c7b9b5f318b166ef4576a
    apex-puppet-tripleo: I231054a433eb7e598a6e24f6eaea02d476e776de

    Change-Id: I4a1f68c75ae3b7d2a5b347d05abf0d025e8b116b
    Signed-off-by: Feng Pan <fpan@redhat.com>