restapi: Don't use @Formatted

This annotation is Resteasy specific, and is no longer needed, as our
custom JAXB message body writer already formats all the XML output.

Change-Id: Ib261291a5b8a2c72c4601f50e6f7cd9f344a4ee1
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>