Add a timeout when running install command in tests
Add a timeout when running install command in tests

A 30 seconds timeout prevents the command from hanging indefinitely, and
would fail instead.

The install command doesn't wait for the installation to complete so it
should be fast under normal circumstances.

kensipe/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli