Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Add a new env var for nameserver

    We should still consider that the nameserver must be handled by all
    installers instead [1]:
      - by configuring one or more DNS resolvers in dhcp_agent.ini
      - by asking a local resolv

    It eases setting the nameserver in testcases and then allows gating
    them. 8.8.8.8 is still defined by default.

    [1] https://docs.openstack.org/neutron/pike/admin/config-dns-res.html

    Co-Authored-By: Cédric Ollivier <cedric.ollivier@orange.com>
    Change-Id: Id58dd5ebee612a0fce2ebc40f089769e60899416
    Signed-off-by: Linda Wang <wangwulin@huawei.com>
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
  - Define a new env var for volume device name

    It eases modifying the volume device name written in tempest config.
    Fuel jobs should be adapted to set the right value (vdc) which
    differs from default (vdb).

    Change-Id: I09212018f94daa800ede815bd3586cceed0d54e7
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index deb36ab..530c678 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit deb36ab8bd9e5f477ee2c0a098ce44567c496e5e
+Subproject commit 530c678677cc314c159936fdf5e121e83fc1d0cc