Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Add "host_name_separator" variable to Context class"
  - Add "host_name_separator" variable to Context class

    This feature will provide Kubernetes context the ability to handle the
    context name inside the class itself, providing to the developer an
    abstraction of the possible naming limitations in Kubernetes. E.g.:
    "dot" character in Pod names is no allowed [1].

    [1] https://github.com/fabric8io/fluent-plugin-kubernetes_metadata_filter/issues/58

    JIRA: YARDSTICK-1188

    Change-Id: I82121f970b550170357a443b6340be7900602a57
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 008e77b..9008c4f 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 008e77b99f31dafa124c6a34724969ef16d5ef7a
+Subproject commit 9008c4f324b368dcd8594b7af76875e9b2720917