Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Adding reference to EXTERNAL_NETWORK to user guide

    Adding a reference to the EXTERNAL_NETWORK environment variable to the
    user guide so that users add this to their env_config.sh. This variable
    is required, among others, to overwrite the default external network in
    Yarstick.

    Change-Id: I50e609a8c6e20b1dd01c61d5d950ffba792e98fa
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index a1f0d26..12207c7 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit a1f0d264158a555aa114d0d60f9a5121d0a0148c
+Subproject commit 12207c749aeee06b805ac1b546e473c7519d96d6