Update git submodules

* Update docs/submodules/appc.git from branch 'master'
  to ca4fa51a8793515b40f0e01ff60e6c77b53e32f6
  - Added test case for RestClient Invoker
    
    Increased the coverage from 0% to 92%
    
    Issue-ID: APPC-1439
    Change-Id: Icb1d51c3b62570e4f4294021b7ea92b325c085ee
    Signed-off-by: Lathishbabu Ganesan <lathishbabu.ganesan@ericsson.com>
    
diff --git a/docs/submodules/appc.git b/docs/submodules/appc.git
index 171a665..ca4fa51 160000
--- a/docs/submodules/appc.git
+++ b/docs/submodules/appc.git
@@ -1 +1 @@
-Subproject commit 171a665f8a9f4b89cf9847e1453a33d1ddfd038c
+Subproject commit ca4fa51a8793515b40f0e01ff60e6c77b53e32f6