Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "trex: Tests with T-Rex in VM"
  - trex: Tests with T-Rex in VM

    Patch introduces a set of testcases with T-Rex running inside VM.

    JIRA: VSPERF-560

    Change-Id: I5b0a0220a2d72428ae1210ee9590d39abdfb9c1d
    Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
    Signed-off-by: RadoslawX Glombiowski <radoslawx.glombiowski@intel.com>
    Reviewed-by: Al Morton <acmorton@att.com>
    Reviewed-by: Christian Trautman <ctrautma@redhat.com>
    Reviewed-by: Sridhar Rao <sridhar.rao@spirent.com>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index 4a4ee67..321da7d 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit 4a4ee678acca263ac39a67068822f3ffee8ecaf2
+Subproject commit 321da7d6f423439dd0772b3c96150e92f484541e