replace fmt.Sprintf("%s:%d") with net.JoinHostPort

[kevinburkesegment]

Several places in the codebase use fmt.Sprintf to join a host and a port, for example:

httpgrpc/server/server.go:118:		address := fmt.Sprintf("kubernetes:///%s%s:%s", service, domain, port)
crypto/tls/test/tls_integration_test.go:109:	httpURL := fmt.Sprintf("https://localhost:%d/hello", httpPort)
crypto/tls/test/tls_integration_test.go:110:	grpcHost := fmt.Sprintf("localhost:%d", grpcPort)
kv/memberlist/memberlist_client_test.go:853:					cfg.JoinMembers = []string{fmt.Sprintf("%slocalhost:%d", testData.queryType, ports[1])}
kv/memberlist/memberlist_client_test.go:933:	cfg.JoinMembers = []string{fmt.Sprintf("127.0.0.1:%d", ports[0])}
kv/memberlist/memberlist_client_test.go:999:				_, err := kv.kv.JoinMembers([]string{fmt.Sprintf("127.0.0.1:%d", portToConnect)})
kv/memberlist/memberlist_client_test.go:1158:	_, err = mkv2.JoinMembers([]string{fmt.Sprintf("127.0.0.1:%d", mkv1.GetListeningPort())})
kv/memberlist/memberlist_client_test.go:1202:	cfg2.JoinMembers = []string{fmt.Sprintf("localhost:%d", ports[0])}
kv/memberlist/memberlist_client_test.go:1433:	cfg.JoinMembers = []string{fmt.Sprintf("127.0.0.1:%d", mkv1.GetListeningPort())}
server/server_tracing_test.go:92:	helloRouteURLRaw := fmt.Sprintf("http://%s:%d/hello", httpAddress, httpPort)
server/server_tracing_test.go:97:	helloPathParamRouteURLRaw := fmt.Sprintf("http://%s:%d/hello/world", httpAddress, httpPort)
server/server.go:251:	httpListener, err := net.Listen(network, fmt.Sprintf("%s:%d", cfg.HTTPListenAddress, cfg.HTTPListenPort))
server/server.go:275:	grpcListener, err := net.Listen(network, fmt.Sprintf("%s:%d", cfg.GRPCListenAddress, cfg.GRPCListenPort))
ring/lifecycler_test.go:515:	assert.Equal(t, fmt.Sprintf("%s:%d", lifecyclerCfg.Addr, lifecyclerCfg.Port), desc.GetAddr())

Because fmt.Sprintf is a general purpose parser, it will be slower than invoking the fit-for-purpose net.JoinHostPort. In addition, net.JoinHostPort correctly handles ipv6 addresses, which can include colons.

I'd be happy to replace all of these just wanted to point this out.

[charleskorn]

Thanks for pointing this out @kevinburkesegment.

I'd be happy to replace all of these

If you'd like to open a PR to fix this, that would be great.