Netty SSL implementation is missing for OC-Agent Trace Exporter

[JonasKunz]

The OC-Agent Trace exporter requires a proper netty-ssl dependency according to it's documentation,
which is currently missing.

This can cause the following problem:

2020-07-09 11:07:41.901  INFO 67275 --- [pool-4-thread-1] io.grpc.netty.GrpcSslContexts            : Jetty ALPN unavailable (this may be normal)
java.lang.ClassNotFoundException: org/eclipse/jetty/alpn/ALPN
            at java.lang.Class.forName0(Native Method)
            at java.lang.Class.forName(Class.java:348)
            at io.grpc.netty.JettyTlsUtil.isJettyAlpnConfigured(JettyTlsUtil.java:64)
            at io.grpc.netty.GrpcSslContexts.findJdkProvider(GrpcSslContexts.java:266)
            at io.grpc.netty.GrpcSslContexts.defaultSslProvider(GrpcSslContexts.java:248)
            at io.grpc.netty.GrpcSslContexts.configure(GrpcSslContexts.java:171)
            at io.grpc.netty.GrpcSslContexts.forClient(GrpcSslContexts.java:120)
            at io.grpc.netty.NettyChannelBuilder.buildTransportFactory(NettyChannelBuilder.java:401)
            at io.grpc.internal.AbstractManagedChannelImplBuilder.build(AbstractManagedChannelImplBuilder.java:444)
            at io.opencensus.exporter.trace.ocagent.OcAgentTraceExporterHandler.getTraceServiceStub(OcAgentTraceExporterHandler.java:117)
            at io.opencensus.exporter.trace.ocagent.OcAgentTraceExporterHandler.timeLimitedExport(OcAgentTraceExporterHandler.java:70)
            at io.opencensus.exporter.trace.util.TimeLimitedHandler$1.call(TimeLimitedHandler.java:91)
            at io.opencensus.exporter.trace.util.TimeLimitedHandler$1.call(TimeLimitedHandler.java:88)
            at java.util.concurrent.FutureTask.run(FutureTask.java:266)
            at rocks.inspectit.ocelot.core.instrumentation.correlation.log.LogTraceCorrelatorImpl.lambda$wrap$1(LogTraceCorrelatorImpl.java:64)
            at io.grpc.Context$1.run(Context.java:595)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)