Update git submodules

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>