Update git submodules

* Update docs/submodules/opera from branch 'master'
  - Clean nfvo-driver-vnfm-juju docker

    nfvo-driver-vnfm-juju docker is unstable and currently
    using a personal docker repository to keep a working
    one. function docker_clean will only clean docker from
    openoint

    Change-Id: I90d5b98a10e44e900fe231e4b29925889536af41
    Signed-off-by: Harry Huang <huangxiangyu5@huawei.com>

diff --git a/docs/submodules/opera b/docs/submodules/opera
index 7ee5c95..7921973 160000 (submodule)
--- a/docs/submodules/opera
+++ b/docs/submodules/opera
@@ -1 +1 @@
-Subproject commit 7ee5c95db62d13d860d51974aa9c0a14404cee56
+Subproject commit 79219733ea099837d77bf851adde66f6e06c1b5e