Fix EZP-20860: Improve unit test code coverage of EzPublishRestBundle

Added unit tests for RestListener::onKernelRequest
Fix EZP-20860: Improve unit test code coverage of EzPublishRestBundle

Added unit tests for RestListener::onKernelResultView
Fix EZP-20860: Improve unit test code coverage of EzPublishRestBundle

Added unit tests for RestListener::onKernelExceptionView