Use net.ParseCIDR instead of custom-built parsers (#3055)

Removes avoidable conversion to and from net.IP to string.

cmd/interface-ips_test.go

@@ -0,0 +1,31 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import "testing"
+
+func TestGetInterfaceIPv4s(t *testing.T) {
+	ipv4s, err := getInterfaceIPv4s()
+	if err != nil {
+		t.Fatalf("Unexpected error %s", err)
+	}
+	for _, ip := range ipv4s {
+		if ip.To4() == nil {
+			t.Fatalf("Unexpected expecting only IPv4 addresses only %s", ip)
+		}
+	}
+}