Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "xci: Rename provision-vm-nodes playbook"
  - xci: Rename provision-vm-nodes playbook

    The provision-vm-nodes playbook doesn't do any VM provisioning. It
    basically just bootstraps the bifrost repository so rename it to
    make it clear what this is about.

    Change-Id: I1c10bc6135686c5197d553a885412a94312a41bc
    Signed-off-by: Markos Chandras <mchandras@suse.de>

diff --git a/docs/submodules/releng-xci b/docs/submodules/releng-xci
index 168fc3e..f06fd87 160000 (submodule)
--- a/docs/submodules/releng-xci
+++ b/docs/submodules/releng-xci
@@ -1 +1 @@
-Subproject commit 168fc3e5e362e9a50300677615c6159f18119689
+Subproject commit f06fd879a8a5f715f410456aad8d32d10a4edea0