Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Define an extra vars path and copy into playbooks"
  - Define an extra vars path and copy into playbooks

    This will allow to define the XCI_EXTRA_VARS_PATH, that can
    contain group_vars/all (or any other valid files), and those
    will be copied inside releng and bifrost playbooks.

    Change-Id: I95e4b0bfb67f26bfa1eb10c97096784eb7f3a87a
    Signed-Off-By: Yolanda Robla <yroblamo@redhat.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index ba53f5c..f25dd3b 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit ba53f5c4a3004b05281079dfe75ff3ab8719c237
+Subproject commit f25dd3b80ec0425684057a30302e8c15827c4e93