Address/Port Concatenation Issue vtadmin (IPv6)

[jordangarside]

➜ kubectl -n vitess logs kiwi-zone1-vtadmin-406d5688-76ff574f6f-qxhd6 -c vtadmin-api
...
W1219 23:35:57.273445       1 component.go:39] [core] [Channel #1 SubChannel #3]
  grpc: addrConn.createTransport failed to connect to {
    Addr: "fd01:10:100:1a01::c0f0:15999", ServerName: "", 
  }. Err: connection error: desc =
  "transport: Error while dialing: dial tcp: address fd01:10:100:1a01::c0f0:15999: too many colons in address"

Bug: The discovery config uses simple string formatting:
"hostname": "%s:%d"

With vtctldServiceIP (the ClusterIP) and port, producing:
fd01:10:100:1a01::c0f0:15999

Fix: Should use net.JoinHostPort() which properly brackets IPv6:
"hostname": net.JoinHostPort(vtctldServiceIP, strconv.Itoa(vtctldServiceGrpcPort))

This would produce the correct format:
[fd01:10:100:1a01::c0f0]:15999

vitess-operator/pkg/controller/vitesscluster/reconcile_vtadmin.go

Lines 289 to 303 in 839329a

	"vtctlds": [
	{
	"host": {
	"fqdn": "%s:%d",
	"hostname": "%s:%d"
	}
	}
	],
	"vtgates": [
	{
	"host": {
	"hostname": "%s:%d"
	}
	}
	]

Not sure exactly which version I'm using, but this is the image digest which appears to be latest as of today:
https://hub.docker.com/layers/planetscale/vitess-operator/latest/images/sha256-459c3570105bb7fa986b6049b733833def40aa47bc787d83d3f656d9082f9737