Target "tests" now only builds the modules tagged as "tests"

But not install them.
This prevents "make tests" polluting system.img or userdata.img.
We have new mechanism to build and package up modules into zip file in
build/core/tasks/tools.
Change package-modules.mk to install DATA/ instead of data/ in the
zip file; Better handle of module name conflicting.

Bug: 13585955
Change-Id: I7586a8c7995b984c9ead0ba2fa84dd5d2dd20bd1