Modules shouldn't be dexpreopted and possibly stripped when
compile_dex is set but installable is not set. This matches the
previous behavior when the dexpreopt rules were in Make.
Bug: 121317615
Test: dexpreopt_test.go
Change-Id: I6f80b7b37a990c475b91aa5d98a19a3baa85eb1b
I6bb2c971cee65d2338839753aa0d84939f335b1b accidentally caused
java_test modules to be dexpreopted and possibly stripped.
Test: dexpreopt_test.go
Change-Id: Ida8f046c509c97e38bd3bce66944d32f01530db4