Illegal character in hostname error when using consul and docker

I'm having microservices running in Docker containers and I use Consul as service discovery. Every now and then the GRPC calls between the services are failing and I get this exception:

```
io.grpc.internal.ProxyDetectorImpl.detectProxy Failed to construct URI for proxy lookup, proceeding without proxy
java.net.URISyntaxException: Illegal character in hostname at index 19: https://xxx2_xx-yyy-zzz_1.www2_ppp:8192
at java.net.URI$Parser.fail(URI.java:2848)
at java.net.URI$Parser.parseHostname(URI.java:3387)
at java.net.URI$Parser.parseServer(URI.java:3236)
at java.net.URI$Parser.parseAuthority(URI.java:3155)
at java.net.URI$Parser.parseHierarchical(URI.java:3097)
at java.net.URI$Parser.parse(URI.java:3053)
at java.net.URI.(URI.java:673)
at io.grpc.internal.ProxyDetectorImpl.detectProxy(ProxyDetectorImpl.java:128)
at io.grpc.internal.ProxyDetectorImpl.proxyFor(ProxyDetectorImpl.java:118)
at io.grpc.internal.InternalSubchannel.startNewTransport(InternalSubchannel.java:207)
at io.grpc.internal.InternalSubchannel.obtainActiveTransport(InternalSubchannel.java:188)
at io.grpc.internal.ManagedChannelImpl$SubchannelImpl.requestConnection(ManagedChannelImpl.java:1130)
at io.grpc.PickFirstBalancerFactory$PickFirstBalancer.handleResolvedAddressGroups(PickFirstBalancerFactory.java:79)
...
```

### What version of gRPC are you using?
1.10.0

### What did you expect to see?
I would expect that when the DNS name contains non-URI friendly characters, the GRPC call to continue to work and encode the URI properly.

Beginne mit io.grpc.internal.ProxyDetectorImpl beim gemeldeten Fehler nahe Zeile 128 und reproduziere dann die Proxy-Suche unter Verwendung des im Stacktrace angezeigten Hostnamens. Als erledigt gilt, dass der gRPC-Aufruf weiterhin funktioniert, wenn der DNS-Name die gemeldeten Zeichen enthält und die URI korrekt verarbeitet wird.

Vom Indexierungsmodell aus dem Issue-Text verfasst.