Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "docs: Update step driven test documentation"
  - docs: Update step driven test documentation

    A minor update of step driven documentation, which should help
    with better understanding of this feature.

    Change-Id: I58d1483f98520a008c8cbea9c820343c33835e6f
    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>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index 67cf875..03c55c5 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit 67cf875fb7548a011aa89799cb814c84513584f5
+Subproject commit 03c55c5804a60b19c182752d38d90a29eefdc84a