Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Bugfix: remove test.dbf file in recovery script"
  - Bugfix: remove test.dbf file in recovery script

    JIRA: YARDSTICK-696

    Change-Id: I09b73079ff828c43040723794115bb07f74242e8
    Signed-off-by: zshi <zshi@redhat.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 9ba594f..79efa6e 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 9ba594fa3f34d551d34abd7582281ce081924c67
+Subproject commit 79efa6e0d975dcd08aa5e29fc645d30601dfe927