That said, your log looks like you're not going to be able to remove the dependency. It's clearly being used.
Caused by: java.lang.NoClassDefFoundError: com/netflix/discovery/converters/XmlXStream
at com.netflix.discovery.converters.wrappers.CodecWrappers$XStreamXml.<init>(CodecWrappers.java:358) ~[eureka-client-1.9.8.jar!/:1.9.8]
at com.netflix.discovery.converters.wrappers.CodecWrappers.create(CodecWrappers.java:133) ~[eureka-client-1.9.8.jar!/:1.9.8]
at com.netflix.discovery.converters.wrappers.CodecWrappers.getCodec(CodecWrappers.java:56) ~[eureka-client-1.9.8.jar!/:1.9.8]
at com.netflix.discovery.converters.wrappers.CodecWrappers.getCodec(CodecWrappers.java:47) ~[eureka-client-1.9.8.jar!/:1.9.8]
at org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration.getFullXml(EurekaServerAutoConfiguration.java:138) ~[spring-cloud-netflix-eureka-server-2.1.1.RELEASE.jar!/:2.1.1.RELEASE]
It maybe that you can change your Eureka server configuration and disable the code that's requiring that dependency. I do not know off hand, and it would likely depend on how you're seeing up your Eureka server. Are you using Spring Cloud Services? Or are you creating the server manually from the OSS project? If it's the latter, could you submit a demo project or something to reproduce the issue you're seeing? I could take a look at it and see if it's possible to work around needing xstream.