Update git submodules

* Update docs/submodules/appc.git from branch 'master'
  to 639f053e8819d76a254f20f5c0b797ee65965301
  - Volume - Junit Test case added
    
    Volume - Junit Test case added
    
    Issue-ID: APPC-1372
    Change-Id: I44a262819ddc3f0f3319e320ef3bf01ef8ca1e13
    Signed-off-by: Sudarshan Kumar <sudars19@in.ibm.com>
    
diff --git a/docs/submodules/appc.git b/docs/submodules/appc.git
index 3a3d8e4..639f053 160000
--- a/docs/submodules/appc.git
+++ b/docs/submodules/appc.git
@@ -1 +1 @@
-Subproject commit 3a3d8e4ff51b849335946ec1cc06aedaa133730b
+Subproject commit 639f053e8819d76a254f20f5c0b797ee65965301