Remove panic() and handle it appropriately (#5807)

This is an effort to remove panic from the source. 
Add a new call called CriticialIf, that calls LogIf and exits. 
Replace panics with one of CriticalIf, FatalIf and a return of error.

cmd/object-api-utils.go

@@ -168,7 +168,7 @@ func pathJoin(elem ...string) string {
 func mustGetUUID() string {
 	uuid, err := uuid.New()
 	if err != nil {
-		panic(fmt.Sprintf("Random UUID generation failed. Error: %s", err))
+		logger.CriticalIf(context.Background(), err)
 	}
 
 	return uuid.String()