Update git submodules

* Update docs/submodules/integration.git from branch 'master'
  to 21b09c956609d3ebee0081686802d20da194c523
  - Improve vCPE test automation
    
    Signed-off-by: Yang Xu <yang.xu@futurewei.com>
    Issue-ID: INT-847
    Change-Id: Ib5b0a547f1c228de4cee02f3526401028c10bff0
    
diff --git a/docs/submodules/integration.git b/docs/submodules/integration.git
index 8f04ed2..21b09c9 160000
--- a/docs/submodules/integration.git
+++ b/docs/submodules/integration.git
@@ -1 +1 @@
-Subproject commit 8f04ed2a73c671717c50a0e27699ac3ff690c2a6
+Subproject commit 21b09c956609d3ebee0081686802d20da194c523