Fix the usage example
Fix the usage example

This fixes the issue #525

Changes:
```
object name changed from 'service' to 'discovery'
line2: method name changed from 'setEndpoint' to 'setEndPoint'
```
JoshSharpe/java-sdk,supunucsc/java-sdk,watson-developer-cloud/java-sdk,watson-developer-cloud/java-sdk,supunucsc/java-sdk,JoshSharpe/java-sdk,JoshSharpe/java-sdk,supunucsc/java-sdk,watson-developer-cloud/java-sdk,watson-developer-cloud/java-sdk