Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Add ablity to config EXTERNAL_NETWORK in env_config.sh

    - EXTERNAL_NETWORK env variable can be explicitly set
    - If set, the value will be used in Yardstack configuration
    - Otherwise, previous method of using output from
    'openstack network list' will still be employed

    Change-Id: I9d8b4a69ff3f5093c034823cc95e92e151bfade6
    Signed-off-by: Eddie Arrage <eddie.arrage@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index e57e406..670362c 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit e57e40687c47c3a50ecaae43e153b2ca8981423c
+Subproject commit 670362c0c12b3595591a824f633f8f3182554be9