Update git submodules

* Update docs/submodules/releng from branch 'master'
  - xci: Enable node provisioning and shuffle/rename stuff

    This change enables node provisioning using bifrost based on the chosen
    flavor.

    Other changes include
    - move flavor specific stuff (playbooks, inventory, vars) into their own
    folders so it is easier to copy them over.
    - rename flavors and get rid of xci from them.
    - introduce env-vars to keep variables that are not really user variables.

    Please note that this patch contains empty files and so on due to still
    trying to find best way to structurei things. Apart from this, there will
    probably be lots of duplications here and there which will be taken care
    of once things settle.

    Change-Id: I04a5d422e5b018439bafea5e68e65255ae38d22b
    Signed-off-by: Fatih Degirmenci <fatih.degirmenci@ericsson.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index eab89fd..1d715c6 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit eab89fda5f0fde5b8c608b7facb3f8d45970a8ec
+Subproject commit 1d715c681a1216b7b91f05a779df6e34b2179cef