Fix a bug that allowed duplicate module names.
Fix a bug that allowed duplicate module names.

Change-Id: I9317e43ac435a26397557328036c11a8a2da7480

colincross/blueprint,yuhangwang/blueprint,danw/blueprint,Tiger66639/blueprint,jgennis/blueprint,colincross/blueprint,jgennis/blueprint,danw/blueprint,Tiger66639/blueprint,yuhangwang/blueprint,google/blueprint,google/blueprint