Integration tests depend on optional "routing" endpoint

[Lokowandtg]

When running the integration tests of cf-java-client, some of them fail because they depend on the routing-api. The routing-api is optional and by default not installed.
The tests should be aware of the installation state (it is reported by a "null" value when calling the "/" endpoint. They should be skipped when the routing-api is not installed.

I will push some corrections.

[Lokowandtg]

Fixed with cloudfoundry#1250 for class ApplicationsTest. Working on verification for other tests.