Update git submodules

* Update docs/submodules/compass4nfv from branch 'stable/danube'
  - Remove ovs-dpdk package

    JIRA: COMPASS-483

    "openvswitch-switch-dpdk" is not useful for current scenarios
    and it will be incompatible with SFC scenarios. So we remove
    it in this patch for the preparation of SFC online.

    Change-Id: If48f63266101f0bc91faaab4ff330eac20e893c8
    Signed-off-by: Yifei Xue <xueyifei@huawei.com>

diff --git a/docs/submodules/compass4nfv b/docs/submodules/compass4nfv
index f20effc..b928c4f 160000 (submodule)
--- a/docs/submodules/compass4nfv
+++ b/docs/submodules/compass4nfv
@@ -1 +1 @@
-Subproject commit f20effca792bb5dfa2898585f3431de5d296064f
+Subproject commit b928c4f50eea276aacebdeb875500e99915e9c92