fix java.lang.IncompatibleClassChangeError with in DeproxyEndpointListen...

Got a strange error when using latest gdeproxy 0.11:

java.lang.IncompatibleClassChangeError: the number of constructors during runtime and compile time for java.lang.Thread do not match. Expected 8 but got 10
   at org.rackspace.gdeproxy.DeproxyEndpoint$DeproxyEndpointListenerThread.<init>(DeproxyEndpoint.groovy:91)
   at org.rackspace.gdeproxy.DeproxyEndpoint.<init>(DeproxyEndpoint.groovy:76)
   at org.rackspace.gdeproxy.Deproxy.addEndpoint(Deproxy.groovy:216)
   at features.services.httpconnectionpool.HttpClientServiceTest.setup(HttpClientServiceTest.groovy:17)

Found this reported bug: http://jira.codehaus.org/browse/GROOVY-5475