fix maven local build issue

onap jenkins use maven-assembly-plugin 2.2-beta-5. without fix, local build use
maven-assembly-plugin 2.4.1 and build fails as:
Assembly is incorrectly configured: null.

to fix local build issue:
1. update to maven-assembly-plugin 2.6
2. add AssemblyId configuration which is needed for assembly >= 2.2

Change-Id: Id929f6ff31beb64e9025346c0bf636d44a5eaa47
Signed-off-by: Guo Ruijing <ruijing.guo@intel.com>