Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "trex: Add support for burst traffic type"
  - trex: Add support for burst traffic type

    Support for burst traffic type was added into T-Rex. This
    traffic type is useful for tests, where a limited number
    of frames should be sent through DUT.

    JIRA: VSPERF-562

    Change-Id: I03b7150e66a0210cce91b20c751b8624c16f951b
    Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
    Reviewed-by: Al Morton <acmorton@att.com>
    Reviewed-by: Christian Trautman <ctrautma@redhat.com>
    Reviewed-by: Sridhar Rao <sridhar.rao@spirent.com>
    Reviewed-by: Richard Elias <richardx.elias@intel.com>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index a3e365e..7e26308 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit a3e365e8b39e4e907870a8224a760591c7371130
+Subproject commit 7e263087c47e471fff47f204e79d7fe21a56eaa9