-unix does not work and expects a port

in grpcurl `./grpcurl -plaintext -unix /var/run/grpc.sock list` does work fine with my server.

But with grpcui it does not start up and outputs an error.

`./grpcui -plaintext -unix /var/run/grpc.sock
Failed to dial target host "/var/run/grpc.sock": connection error: desc = "transport: error while dialing: dial tcp: address /var/run/grpc.sock: missing port in address"`

Reproduce the grpcui invocation with `-plaintext -unix /var/run/grpc.sock` and compare its behavior with the working grpcurl command. Trace the command-line handling for the `-unix` target and verify completion when grpcui connects without reporting a missing port.

Written by the indexing model from the issue text.