Proxy client throws UnsupportedOperationException when calling hashCode()

In application tear-down phase, Spring Data JPA uses a remove() method on a ConcurrentHashMap (that's why it needs hashCode()) to close all entityManagers. This method is called for each registered bean, therefore the proxy clients as well. The proxy client throws UnsupportedOperationException.

Stack trace:

```
java.lang.UnsupportedOperationException: Not a resource method.
at org.glassfish.jersey.client.proxy.WebResourceFactory.invoke(WebResourceFactory.java:189) ~[jersey-proxy-client-2.22.2.jar:na]
at com.sun.proxy.$Proxy145.hashCode(Unknown Source) ~[na:na]
at java.util.concurrent.ConcurrentHashMap.hash(ConcurrentHashMap.java:333) ~[na:1.7.0_79]
at java.util.concurrent.ConcurrentHashMap.remove(ConcurrentHashMap.java:1175) ~[na:1.7.0_79]
at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.postProcessBeforeDestruction(PersistenceAnnotationBeanPostProcessor.java:374) ~[spring-orm-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.DisposableBeanAdapter.destroy(DisposableBeanAdapter.java:243) ~[spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroyBean(DefaultSingletonBeanRegistry.java:578) [spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingleton(DefaultSingletonBeanRegistry.java:554) [spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingleton(DefaultListableBeanFactory.java:972) [spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingletons(DefaultSingletonBeanRegistry.java:523) [spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingletons(DefaultListableBeanFactory.java:979) [spring-beans-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.destroyBeans(AbstractApplicationContext.java:1006) [spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:982) [spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext$1.run(AbstractApplicationContext.java:901) [spring-context-4.2.6.RELEASE.jar:4.2.6.RELEASE]
```

This is very similar to #2996 and it is mentioned [here](https://java.net/jira/browse/JERSEY-2724?focusedCommentId=391107&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-391107)
#### Affected Versions
[2.22.2]