opentelemetry-java-instrumentation: Metric export fails

Current version prints the following exception during runtime:

[opentelemetry.auto.trace 2020-08-27 09:57:28:819 +0300] [grpc-default-executor-0] WARN io.opentelemetry.exporters.otlp.OtlpGrpcMetricExporter - Failed to export spans
io.grpc.StatusRuntimeException: UNIMPLEMENTED: unknown service opentelemetry.proto.collector.metrics.v1.MetricsService
	at io.grpc.Status.asRuntimeException(Status.java:533)
	at io.grpc.stub.ClientCalls$UnaryStreamToFuture.onClose(ClientCalls.java:515)
	at io.grpc.PartialForwardingClientCallListener.onClose(PartialForwardingClientCallListener.java:39)
	at io.grpc.ForwardingClientCallListener.onClose(ForwardingClientCallListener.java:23)
	at io.grpc.ForwardingClientCallListener$SimpleForwardingClientCallListener.onClose(ForwardingClientCallListener.java:40)
	at io.grpc.internal.CensusStatsModule$StatsClientInterceptor$1$1.onClose(CensusStatsModule.java:700)
	at io.grpc.PartialForwardingClientCallListener.onClose(PartialForwardingClientCallListener.java:39)
	at io.grpc.ForwardingClientCallListener.onClose(ForwardingClientCallListener.java:23)
	at io.grpc.ForwardingClientCallListener$SimpleForwardingClientCallListener.onClose(ForwardingClientCallListener.java:40)
	at io.grpc.internal.CensusTracingModule$TracingClientInterceptor$1$1.onClose(CensusTracingModule.java:399)
	at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:510)
	at io.grpc.internal.ClientCallImpl.access$300(ClientCallImpl.java:66)
	at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.close(ClientCallImpl.java:630)
	at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.access$700(ClientCallImpl.java:518)
	at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInternal(ClientCallImpl.java:692)
	at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInContext(ClientCallImpl.java:681)
	at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
	at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:123)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:834)