fix .travis.yml for code coverage
fix .travis.yml for code coverage

redtankd/github-test,redtankd/rust-test,redtankd/rust-test,redtankd/rust-test,redtankd/github-test,redtankd/github-test,redtankd/rust-test,redtankd/github-test,redtankd/rust-test,redtankd/rust-test