Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - [ovs/dpdk] Turn on non-blocking ovs calls

    Change-Id: I8206707cdb2ebc267b6f4971de35477e3dc73c5f
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index ab31c13..6d39512 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit ab31c13580dc51bb95d07627da5b19216ef2edff
+Subproject commit 6d3951219e31c0fe50bee1489fb0a5124e9921f6