Allow server to start if one of local nodes in docker/kubernetes setup is resolved (#7452)

Allow server to start if one of the local nodes in docker/kubernetes setup is successfully resolved

- The rule is that we need atleast one local node to work. We dont need to resolve the
  rest at that point.

- In a non-orchestrational setup, we fail if we do not have atleast one local node up
  and running.

- In an orchestrational setup (docker-swarm and kubernetes), We retry with a sleep of 5
  seconds until any one local node shows up.

Fixes #6995

cmd/net.go

@@ -17,7 +17,6 @@
 package cmd
 
 import (
-	"context"
 	"errors"
 	"fmt"
 	"net"
@@ -27,9 +26,7 @@ import (
 	"strconv"
 	"strings"
 	"syscall"
-	"time"
 
-	humanize "github.com/dustin/go-humanize"
 	"github.com/minio/minio-go/pkg/set"
 	"github.com/minio/minio/cmd/logger"
 )
@@ -102,40 +99,7 @@ func getHostIP(host string) (ipList set.StringSet, err error) {
 	var ips []net.IP
 
 	if ips, err = net.LookupIP(host); err != nil {
-		// return err if not Docker or Kubernetes
-		// We use IsDocker() method to check for Docker Swarm environment
-		// as there is no reliable way to clearly identify Swarm from
-		// Docker environment.
-		if !IsDocker() && !IsKubernetes() {
-			return ipList, err
-		}
-
-		// channel to indicate completion of host resolution
-		doneCh := make(chan struct{})
-		// Indicate retry routine to exit cleanly, upon this function return.
-		defer close(doneCh)
-		// Mark the starting time
-		startTime := time.Now()
-		// wait for hosts to resolve in exponentialbackoff manner
-		for range newRetryTimerSimple(doneCh) {
-			// Retry infinitely on Kubernetes and Docker swarm.
-			// This is needed as the remote hosts are sometime
-			// not available immediately.
-			if ips, err = net.LookupIP(host); err == nil {
-				break
-			}
-			// time elapsed
-			timeElapsed := time.Since(startTime)
-			// log error only if more than 1s elapsed
-			if timeElapsed > time.Second {
-				// log the message to console about the host not being
-				// resolveable.
-				reqInfo := (&logger.ReqInfo{}).AppendTags("host", host)
-				reqInfo.AppendTags("elapsedTime", humanize.RelTime(startTime, startTime.Add(timeElapsed), "elapsed", ""))
-				ctx := logger.SetReqInfo(context.Background(), reqInfo)
-				logger.LogIf(ctx, err)
-			}
-		}
+		return ipList, err
 	}
 
 	ipList = set.NewStringSet()