Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Remove tool provisioning from DpdkVnfSetupEnvHelper._setup_dpdk"
  - Remove tool provisioning from DpdkVnfSetupEnvHelper._setup_dpdk

    Both "uio" and "igb_uio" drivers are present in the VM image generated
    using "./nsb_setup.sh" script. "igb_uio" driver is compiled along with
    the DPDK library compilation.

    Tool "nsb_setup.sh" provisioning and execution should be removed from
    this function because there is not needed anymore.

    In case "igb_uio" driver is not loaded, an exception should be raised.

    JIRA: YARDSTICK-999

    Change-Id: I89174f84ac36d8231587402c96751746cb18e290
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index a301d17..2550ba0 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit a301d172e9b7df272a882e88407c8e14cfed2b62
+Subproject commit 2550ba07ae7596e928ff574c9b41ed3b977163f6