Fix data race when connecting disks (#11983)
Fix data race when connecting disks (#11983)

Multiple disks from the same set would be writing concurrently.

```
WARNING: DATA RACE
Write at 0x00c002100ce0 by goroutine 166:
  github.com/minio/minio/cmd.(*erasureSets).connectDisks.func1()
      d:/minio/minio/cmd/erasure-sets.go:254 +0x82f

Previous write at 0x00c002100ce0 by goroutine 129:
  github.com/minio/minio/cmd.(*erasureSets).connectDisks.func1()
      d:/minio/minio/cmd/erasure-sets.go:254 +0x82f

Goroutine 166 (running) created at:
  github.com/minio/minio/cmd.(*erasureSets).connectDisks()
      d:/minio/minio/cmd/erasure-sets.go:210 +0x324
  github.com/minio/minio/cmd.(*erasureSets).monitorAndConnectEndpoints()
      d:/minio/minio/cmd/erasure-sets.go:288 +0x244

Goroutine 129 (finished) created at:
  github.com/minio/minio/cmd.(*erasureSets).connectDisks()
      d:/minio/minio/cmd/erasure-sets.go:210 +0x324
  github.com/minio/minio/cmd.(*erasureSets).monitorAndConnectEndpoints()
      d:/minio/minio/cmd/erasure-sets.go:288 +0x244
```
donatello/minio,NitishT/minio,donatello/minio,minio/minio,vadmeste/minio,balamurugana/minio,krisis/minio,NitishT/minio,krisis/minio,NitishT/minio,minio/minio,balamurugana/minio,NitishT/minio,vadmeste/minio