Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Rename the external network for fuel

    The external network was renamend with the MCP deploy to floating_net

    Change-Id: I73f5f5d14b0b18a2e838dae163dcfd62edcb0c0b
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 31af28e..3935025 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 31af28e0d656645a6737c803d019d443d82e34d6
+Subproject commit 3935025adda5f426b968304aca9183165935479f