Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Committing the test case requirements specification to GIT for committer review.

    This doucment needs to be +2'd by the majority of committers prior to merging
    to ensure we are all in agreement with regard to the test case requirements.
    This is a pre-requisite to test case selection for the CVP.

    Updated by dneary 2017-04-25: List formatting, and reorganising requirements for installer and stack composition.

    Change-Id: Iabaf11bc9479a20a58f985233d460013e4690d7c
    Signed-off-by: ChristopherPrice <christopher.price@ericsson.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index 2fbc073..7a9ad80 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit 2fbc0733dbcebb9d3155775e7001977f909ffd50
+Subproject commit 7a9ad808527d29ceaeea584ae3fcef701a8cc58a