xds/interop: update RPC timeout in blackhole after fallback case (#5174)
xds/interop: update RPC timeout in blackhole after fallback case (#5174)


stanley-cheung/grpc-go,dfawley/grpc-go,grpc/grpc-go,dfawley/grpc-go,menghanl/grpc-go,menghanl/grpc-go,stanley-cheung/grpc-go,grpc/grpc-go