Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "prototypes: bifrost: Remove OPNFV specific group_vars file"
  - prototypes: bifrost: Remove OPNFV specific group_vars file

    The only reason we had this file was because we had to define our own
    'ssh_public_key_path' variable to look in the /root directory since we
    were running everything as root. Since we are now moving away from this
    approach, this file is not needed anymore.

    Change-Id: Ic938c4c8c877c95ce261721dc32fc5147081e236
    Signed-off-by: Markos Chandras <mchandras@suse.de>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 3de601e..679c6f7 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 3de601e2194286afae4d44641508330032c6bded
+Subproject commit 679c6f76d09a386ce4d9d08ad85e59490b829d50