Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "xci: Adapt jobs to use common prepare-tests role"
  - xci: Adapt jobs to use common prepare-tests role

    In order to activate more test tiers from functest and also
    start running yardstick, we need to do the test preparation
    at one go and then run what's supposed to be run.

    This change is required for below changes to be verified
    successfully
        https://gerrit.opnfv.org/gerrit/#/c/61639/
        https://gerrit.opnfv.org/gerrit/#/c/61641/

    Change-Id: Ib3ae2241921383b77c23b05443325aa6240cc176
    Signed-off-by: Fatih Degirmenci <fdegir@gmail.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 9c32082..cad73d7 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 9c320823c2898c98628c8537c02d112a3f72d439
+Subproject commit cad73d7ba7dffe634c389f9c8eaea9a97ba9b58d