server: Add more elaborate startup messages. (#2731)

These messages based on our prep stage during XL
and prints more informative message regarding
drive information.

This change also does a much needed refactoring.

cmd/server-startup-msg_test.go

@@ -0,0 +1,34 @@
+/*
+ * 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"
+
+// Tests if we generate storage info.
+func TestStorageInfoMsg(t *testing.T) {
+	obj, _, err := prepareXL()
+	if err != nil {
+		t.Fatal("Unable to initialize XL backend", err)
+	}
+	objLayerMutex.Lock()
+	globalObjectAPI = obj
+	objLayerMutex.Unlock()
+
+	if msg := getStorageInfoMsg(); msg == "" {
+		t.Fatal("Empty message string is not implemented")
+	}
+}