Update git submodules

* Update docs/submodules/storperf from branch 'stable/danube'
  - Pinning version of Swagger UI

    Changes the inclusion of Swagger UI to become a git checkout
    of a fixed version rather than following the head.

    Change-Id: I30def6d6c37a166cc37f15857a98064c760eb7c6
    JIRA: STORPERF-123
    Signed-off-by: mbeierl <mark.beierl@dell.com>
    (cherry picked from commit 67ef3ea942d5d2eaff46572936f12d4ccab4d89c)

diff --git a/docs/submodules/storperf b/docs/submodules/storperf
index cd5a14e..a3c3e7f 160000 (submodule)
--- a/docs/submodules/storperf
+++ b/docs/submodules/storperf
@@ -1 +1 @@
-Subproject commit cd5a14eff5b0c4814230004e56fadea4ab6cba25
+Subproject commit a3c3e7ff26f4d86d0b0084647a333a0fa794ccd5