Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Add sshpass lib for Suse distros

    This patch completes https://gerrit.opnfv.org/gerrit/#/c/52191

    Change-Id: I35259bdcbdb67237576d7b9b6957266c48f6309f
    Signed-off-by: Jose Lausuch <jalausuch@suse.com>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index ba48693..a3d6f14 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit ba486932a77eb7b1ae2f1fd6b3e231df925887e7
+Subproject commit a3d6f14ae861ed8320288f5068ca091c4abf0b7a