We have contacted CA Support and got confirmation that the issue in WSDL in 15.4 and 15.3. There is workaround also available
Below is the recommended workaround
#1 For most if not all WSDL definitions, especially for existing objects, this was the only change. Therefore it is possible to use the generated classes/code from the service defined on the 15.2.0 and earlier releases, and login/run them against 15.3.0 and up.
#2 Alternatively, on the /niku/wsdl pages for 15.3.0+, download each of the .xsd files to be consumed. Edit the files to change the namespace from xog to tns in the message part above. Generate the classes against that.
- Balaji