Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Merge "refstack: add manually method to let user can set its tempest.conf and defcore.txt"
  - refstack: add manually method to let user can set its tempest.conf and defcore.txt

    JIRA: DOVETAIL-394

    for refstack, userguide is listed in https://gerrit.opnfv.org/gerrit/#/c/33049/
    in CI, use the automate way to generate tempest.conf to let refstack run against SUT, i.e., defcore.tc001.yml
    will provide a way to let user can let refstack run against SUT manually, i.e. defcore.tc002.yml
    since the tempest.conf autometely generated may not satisfied with SUT, users can adjust its tempest.conf to let the defcore testcases pass.

    Change-Id: I5ed212c9c6d864d352d1c497ea039cc553461158
    Signed-off-by: MatthewLi <matthew.lijun@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index ac766b0..52503b8 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit ac766b065a8032e4aa90dafef2130292364a2483
+Subproject commit 52503b8bca1025a3412385b45591999530cedc40