Update git submodules

* Update docs/submodules/nfvbench from branch 'master'
  - [NFVBENCH-70] Update nfvbenchvm to 0.6

    1. Update kernel to 4.4.118-1.el7.elrepo.x86_64;
    2. Update to build testpmd off DPDK 18.02;
    3. Update txd/rxd of testpmd to 256/1024;
    4. Update VPP to 17.10-9~gd594711~b55.x86_64;

    Change-Id: I1321b306143d1daf81f8a984ad7739a980c5cfb9
    Signed-off-by: Yichen Wang <yicwang@cisco.com>

diff --git a/docs/submodules/nfvbench b/docs/submodules/nfvbench
index e275e0b..5436500 160000 (submodule)
--- a/docs/submodules/nfvbench
+++ b/docs/submodules/nfvbench
@@ -1 +1 @@
-Subproject commit e275e0bc2ae9ea1906190d81c9e78e85265734df
+Subproject commit 54365002e932743f693af28d3f568c20a9e18513