Don't cache bazel directories on Travis.
Don't cache bazel directories on Travis.

As reported in https://github.com/google/dagger/commit/b06e382b480e25befa2ca1f3aa43cb589b392346#commitcomment-21970278, this seems to be not working (and sometimes even breaking).

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=154749423

ronshapiro/dagger,google/dagger,cgruber/dagger,ronshapiro/dagger,google/dagger,ze-pequeno/dagger,ronshapiro/dagger,hansonchar/dagger,dushmis/dagger,ze-pequeno/dagger,ze-pequeno/dagger,google/dagger,cgruber/dagger,ze-pequeno/dagger,hansonchar/dagger,hansonchar/dagger,google/dagger,cgruber/dagger,dushmis/dagger