Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Add scale out TCs with availability zone support

    Add PROX and vFW scale out TCs with availability zone
    configuration. To be able to specify the availability
    zone for specific VNF or TG the following example of
    command line option shoud be used:

      yardstick -d task start --task-args='{
        "num_vnfs": 2, "availability_zone":
         {
          "vnf_0": "az_0", "tg_0": "az_0",
          "vnf_1": "az_1", "tg_1": "az_1",
          ... }}' <SCALE-OUT-TC-FILE>

    The steps to run new scale-out TCs is documented in the
    userguide.

    JIRA: YARDSTICK-1203

    Change-Id: Ib3878485c5483981fe9b48ab02995712bcc31ae5
    Signed-off-by: Mytnyk, Volodymyr <volodymyrx.mytnyk@intel.com>
    (cherry picked from commit 0156b5c37e08f91a37dda08edb854758bbba7413)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index ab9af28..1d1c746 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit ab9af285f2fce475c2389f15696e2800a0010f0c
+Subproject commit 1d1c746e56bf498054bcc21d1635f8958ac0b9c4