Correctly set the authority to the host rather than scheme (#637)

Sources/GRPC/ClientCalls/BidirectionalStreamingCall.swift

@@ -58,7 +58,7 @@ public final class BidirectionalStreamingCall<RequestMessage: Message, ResponseM
     let requestHead = GRPCRequestHead(
       scheme: connection.configuration.httpProtocol.scheme,
       path: path,
-      host: connection.configuration.httpProtocol.scheme,
+      host: connection.configuration.target.host,
       requestID: requestID,
       options: callOptions
     )

Sources/GRPC/ClientCalls/ClientStreamingCall.swift

@@ -62,7 +62,7 @@ public final class ClientStreamingCall<RequestMessage: Message, ResponseMessage:
     let requestHead = GRPCRequestHead(
       scheme: connection.configuration.httpProtocol.scheme,
       path: path,
-      host: connection.configuration.httpProtocol.scheme,
+      host: connection.configuration.target.host,
       requestID: requestID,
       options: callOptions
     )

Sources/GRPC/ClientCalls/ServerStreamingCall.swift

@@ -50,7 +50,7 @@ public final class ServerStreamingCall<RequestMessage: Message, ResponseMessage:
     let requestHead = GRPCRequestHead(
       scheme: connection.configuration.httpProtocol.scheme,
       path: path,
-      host: connection.configuration.httpProtocol.scheme,
+      host: connection.configuration.target.host,
       requestID: requestID,
       options: callOptions
     )

Sources/GRPC/ClientCalls/UnaryCall.swift

@@ -59,7 +59,7 @@ public final class UnaryCall<RequestMessage: Message, ResponseMessage: Message>
     let requestHead = GRPCRequestHead(
       scheme: connection.configuration.httpProtocol.scheme,
       path: path,
-      host: connection.configuration.httpProtocol.scheme,
+      host: connection.configuration.target.host,
       requestID: requestID,
       options: callOptions
     )