Eliminate the use of xtend

test-provider includes 320 lines of xtend code, which should be easily convertable to Java:

84 ./test-provider/src/main/java/org/opendaylight/openflowplugin/test/OpenflowpluginTestServiceProvider.xtend
84 ./test-provider/src/main/java/org/opendaylight/openflowplugin/test/OpenflowpluginMeterTestServiceProvider.xtend
69 ./test-provider/src/main/java/org/opendaylight/openflowplugin/test/OpenflowpluginTestActivator.xtend
81 ./test-provider/src/main/java/org/opendaylight/openflowplugin/test/OpenflowpluginGroupTestServiceProvider.xtend
318 total

Rewrite these classes in pure java and eliminate the xtend dependency.