Update git submodules

* Update docs/submodules/releng from branch 'master'
  - xci: Disable Centos jobs until Intel lab is back

    Due to Intel lab maintenance, the number of slaves will go down so we need
    to have fewer jobs running. Centos is known to be problematic upstream and
    it is better to disable them until the lab is back online to ensure the jobs
    for other distros are impacted less.

    Change-Id: Ifd8624e45282d68bd7acdf283ef7a499e81990e9
    Signed-off-by: Fatih Degirmenci <fdegir@gmail.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 51a7113..8c1e5d2 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 51a7113c8e7be8b2287641dea7a8a227fc02daa2
+Subproject commit 8c1e5d21f6633c38fba0e97791b837f4691d952e