Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - bifrost: Add ability to pin Ironic-{,client,inspector,inspector-client} SHAs

    We should pin the SHAs for Ironic components as part of the regular
    bifrost bump to ensure maximum long term stability. This also bumps
    the bifrost SHA to the latest available one.

    Change-Id: Ia66d8ab6566db58e2ddab5134eb8445bd84d2a8f
    Signed-off-by: Markos Chandras <mchandras@suse.de>

diff --git a/docs/submodules/releng-xci b/docs/submodules/releng-xci
index 6a14f2d..884c8bb 160000 (submodule)
--- a/docs/submodules/releng-xci
+++ b/docs/submodules/releng-xci
@@ -1 +1 @@
-Subproject commit 6a14f2dcc9f6ebce6800aa22f3517caa0a0962be
+Subproject commit 884c8bbced3fe5320cdb08629343b22ec859aeaf