Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "xci: infra: bifrost: Allow DNS overrides"
  - xci: infra: bifrost: Allow DNS overrides

    Deployers may want to use a different DNS server so allow them to
    override the ipv4_nameserver option. If the variable is not set,
    then we use the libvirt DNS if we are behind a proxy, otherwise
    we default to the Google DNS.

    Change-Id: I96cf63758902d4aae3d155b2e8beef650449ebc9
    Signed-off-by: Markos Chandras <mchandras@suse.de>

diff --git a/docs/submodules/releng-xci b/docs/submodules/releng-xci
index b0eb8e1..afc3c2a 160000 (submodule)
--- a/docs/submodules/releng-xci
+++ b/docs/submodules/releng-xci
@@ -1 +1 @@
-Subproject commit b0eb8e17350baf0b6d71045c7ec5fbfead6560f6
+Subproject commit afc3c2a4cb16b7fd29c1ceec6c4b7f566767dc6b