Add negative test for namespace containsKey method.
Add negative test for namespace containsKey method.

splunk/splunk-sdk-java,dkelmer/splunk-sdk-java,dkelmer/splunk-sdk-java,splunk/splunk-sdk-java,dkelmer/splunk-sdk-java,splunk/splunk-sdk-java,dkelmer/splunk-sdk-java,splunk/splunk-sdk-java,dkelmer/splunk-sdk-java,splunk/splunk-sdk-java,splunk/splunk-sdk-java