[GH-1240] main: Print keys after init and full server initialization.

Setting MINIO_ACCESS_KEY and MINIO_SECRET_KEY re-writes the values
in config properly, but the init message is not updated.

Fix it by delay printing keys until everything is properly
initialized.

api-auth-utils.go

@@ -40,7 +40,7 @@ func isValidAccessKey(accessKeyID string) bool {
 
 // isValidSecretKey - validate secret key
 func isValidSecretKey(secretKeyID string) bool {
-	regex := regexp.MustCompile("^[a-zA-Z0-9\\-\\.\\_\\~]{40}$")
+	regex := regexp.MustCompile("^.{40}$")
 	return regex.MatchString(secretKeyID)
 }