Implement mgmt REST APIs for heal subcommands (#3533)

The heal APIs supported in this change are,
- listing of objects to be healed.
- healing a bucket.
- healing an object.

cmd/xl-v1-healing-common_test.go

@@ -1,5 +1,5 @@
 /*
- * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ * Minio Cloud Storage, (C) 2016, 2017 Minio, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -75,7 +75,7 @@ func TestCommonTime(t *testing.T) {
 	// common modtime. Tests fail if modtime does not match.
 	for i, testCase := range testCases {
 		// Obtain a common mod time from modTimes slice.
-		ctime := commonTime(testCase.times)
+		ctime, _ := commonTime(testCase.times)
 		if testCase.time != ctime {
 			t.Fatalf("Test case %d, expect to pass but failed. Wanted modTime: %s, got modTime: %s\n", i+1, testCase.time, ctime)
 		}