Add reva-gateway endpoint to service discovery

Reva can't be wrapped as a go-micro service due to private apis. We workaround byy manually registering the address and port in the service-registry.

go.mod

@@ -8,6 +8,8 @@ require (
 	github.com/gofrs/uuid v3.2.0+incompatible
 	github.com/gopherjs/gopherjs v0.0.0-20181103185306-d547d1d9531e // indirect
 	github.com/micro/cli/v2 v2.1.1
+	github.com/micro/go-micro v1.18.0
+	github.com/micro/go-micro/v2 v2.0.0
 	github.com/oklog/run v1.0.0
 	github.com/owncloud/ocis-pkg/v2 v2.0.1
 	github.com/pelletier/go-toml v1.6.0 // indirect
@@ -23,3 +25,5 @@ require (
 	gopkg.in/ini.v1 v1.51.1 // indirect
 	gopkg.in/yaml.v2 v2.2.7 // indirect
 )
+
+replace google.golang.org/grpc => google.golang.org/grpc v1.26.0