PubSubBinderConfiguration is not disabled when PubSub is disabled

[markusheiden]

Describe the bug
When using com.google.cloud:spring-cloud-gcp-starter-bus-pubsub on the classpath and disable it in the application.yml via

spring:
  cloud:
    gcp:
      core.enabled: true
      pubsub.enabled: true

the startup fails with Parameter 0 of method pubSubChannelProvisioner in com.google.cloud.spring.stream.binder.pubsub.config.PubSubBinderConfiguration required a bean of type 'com.google.cloud.spring.pubsub.PubSubAdmin' that could not be found.

[ttomsu]

Yep, this looks like an issue. I'll fix it in the new repo and backport it here. Thanks for finding and filing!