Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - xci: xci-lib.sh: Use the OSA requirements file for pip components

    OpenStack-Ansible maintains a requirements file which ensure that a
    working combination of pip/setuptools/wheels/virtualenv can be mixed up
    with distro packages so it's beneficial to take that into consideration
    when building our environment.

    Change-Id: Ic5398de3e464e1526f8d9fb6b6460907ac30084a
    Signed-off-by: Markos Chandras <mchandras@suse.de>

diff --git a/docs/submodules/releng-xci b/docs/submodules/releng-xci
index 9d9d9a4..5c15c8f 160000 (submodule)
--- a/docs/submodules/releng-xci
+++ b/docs/submodules/releng-xci
@@ -1 +1 @@
-Subproject commit 9d9d9a4d6031fe795b8d3dbd71250f676a4180d4
+Subproject commit 5c15c8fe84d4f7e878266fa3a9e98704ab62ddfb