Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Support to specify the valid external network name

    In some deployments, the retrieved external network by the
    def get_external_networks in Snaps checked by "router:external"
    is not available. So it is necessary to specify the available
    external network as an env by user.

    Change-Id: I333e91dd106ed307541a9a197280199fde86bd30
    Signed-off-by: Linda Wang <wangwulin@huawei.com>
    (cherry picked from commit aa7109d038a86f6a19a9fb4af96bd1199cd81330)

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 0642156..3b80954 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 06421562d075f6e9d12a0b43e1dce1982b035d59
+Subproject commit 3b80954f3caf36a957e7193db793ce318d51e58c