Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "utils/fetch_os_creds.sh: Fuel: Robust creds fetch"
  - utils/fetch_os_creds.sh: Fuel: Robust creds fetch

    In case ctl01 node is down, the current mechanism will return
    invalid data (the string "Minion") instead of a valid controller IP.

    Since "keystonercv3" is present on all controller nodes at </root>,
    adjust the credentials fetch to use the first online controller node.

    Change-Id: I4ba15bb40d465b112c5e9fc827e3e2a69e671b26
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 0a912f7..6be64db 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 0a912f7e971082012563150933456fac209049a4
+Subproject commit 6be64db117f494bdb6d59b17676e5341c2f9c3a9