Avoid running javadoc:jar if build fails (#192)
Avoid running javadoc:jar if build fails (#192)

In Travis, all steps in the `script` run regardless if the previous one failed. This makes it harder to find the error when the build fails.
Avoid this issue by using a single step in the `script`.
GoogleCloudPlatform/cloud-spanner-r2dbc,GoogleCloudPlatform/cloud-spanner-r2dbc,GoogleCloudPlatform/cloud-spanner-r2dbc