Update git submodules

* Update docs/submodules/vswitchperf from branch 'stable/danube'
  - Removed Indices

    Change-Id: I57420dfca1a2113ebc35faded3084116c670dbc1
    Signed-off-by: Trevor Cooper <trevor.cooper@intel.com>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index fade001..815edb9 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit fade0012b58649f95bd42d9384235c86cb996543
+Subproject commit 815edb966a5c7c1c82083c7e726885d08cf5e241