Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "Doc: Documentation of Additional tools configuration."
  - Doc: Documentation of Additional tools configuration.

    This patch adds tools.rst under docs/testing/user/configguide.
    tools.rst include documentation of installing and configuring
    Collectors, Loadgens and LLC-Cache Management.
    Changed Interested to Interesting and updated barometer info.

    Change-Id: Id8de4d25619780636d242a04304696f4093b4c07
    Signed-off-by: Sridhar K. N. Rao <sridhar.rao@spirent.com>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index 7e26308..1b37c72 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit 7e263087c47e471fff47f204e79d7fe21a56eaa9
+Subproject commit 1b37c72a4f4459a7e776503e8bb74e393b246493