Update git submodules

* Update docs/submodules/nfvbench from branch 'stable/fraser'
  - Change nfvbench git checkout to stable/fraser in Dockerfile

    Change-Id: I206bc8d0d06e429fd632a37f80c89b16664c8443
    Signed-off-by: ahothan <ahothan@cisco.com>
  - [NFVBENCH-83] Add option to display status and to cleanup

    Change-Id: If135fedee4e5ee9226a262800917c4c35bc83bc7
    Signed-off-by: ahothan <ahothan@cisco.com>
    (cherry picked from commit 6226413ca6e1b4c3a52a3deeb66f8f487c2704ae)

  - NFVBENCH-80 latency stream for IMIX uses 1518B frames

    Change-Id: Ie37202001816ec0b9a8f3ecc08c7ec8c097a5d61
    Signed-off-by: Kerim Gokarslan <kgokarsl@cisco.com>
    (cherry picked from commit d462cb16e8d33fc5c6e79ad05222db799c10d5a5)

  - [NFVBENCH-81]With some Intel X710 NIC cards, NFVbench reports erroneous RX counters

    Work around this NIC FW issue by using port level stats for packets/bytes
    ALso fix mutliple calls to get_stats()

    Change-Id: Id19086d0db6bcc4417adff4ed4ce9606ffb30fe2
    Signed-off-by: ahothan <ahothan@cisco.com>
    (cherry picked from commit 90e69f01d75a76dbac971174db0e701ebd40f543)

  - NFVBENCH-79 TRex latency stats requires at least 18B payload size

    Change-Id: I4add34e853d5b5a37efc877eb183a1fdc622d78a
    Signed-off-by: Kerim Gokarslan <kgokarsl@cisco.com>
    (cherry picked from commit 5d582aada32e1c5f43601015660b7936013f5b30)

diff --git a/docs/submodules/nfvbench b/docs/submodules/nfvbench
index 6226413..c840208 160000 (submodule)
--- a/docs/submodules/nfvbench
+++ b/docs/submodules/nfvbench
@@ -1 +1 @@
-Subproject commit 6226413ca6e1b4c3a52a3deeb66f8f487c2704ae
+Subproject commit c8402089ad8686a16ad08ce6c6e16a14c3144d64