Move admin APIs to new path and add redesigned heal APIs (#5351)

- Changes related to moving admin APIs
   - admin APIs now have an endpoint under /minio/admin
   - admin APIs are now versioned - a new API to server the version is
     added at "GET /minio/admin/version" and all API operations have the
     path prefix /minio/admin/v1/<operation>
   - new service stop API added
   - credentials change API is moved to /minio/admin/v1/config/credential
   - credentials change API and configuration get/set API now require TLS
     so that credentials are protected
   - all API requests now receive JSON
   - heal APIs are disabled as they will be changed substantially

- Heal API changes
   Heal API is now provided at a single endpoint with the ability for a
   client to start a heal sequence on all the data in the server, a
   single bucket, or under a prefix within a bucket.

   When a heal sequence is started, the server returns a unique token
   that needs to be used for subsequent 'status' requests to fetch heal
   results.

   On each status request from the client, the server returns heal result
   records that it has accumulated since the previous status request. The
   server accumulates upto 1000 records and pauses healing further
   objects until the client requests for status. If the client does not
   request any further records for a long time, the server aborts the
   heal sequence automatically.

   A heal result record is returned for each entity healed on the server,
   such as system metadata, object metadata, buckets and objects, and has
   information about the before and after states on each disk.

   A client may request to force restart a heal sequence - this causes
   the running heal sequence to be aborted at the next safe spot and
   starts a new heal sequence.

cmd/test-utils_test.go

@@ -497,6 +497,17 @@ func resetGlobalStorageEnvs() {
 	globalRRStorageClass = storageClass{}
 }
 
+// reset global heal state
+func resetGlobalHealState() {
+	globalAllHealState.Lock()
+	defer globalAllHealState.Unlock()
+	for _, v := range globalAllHealState.healSeqMap {
+		if !v.hasEnded() {
+			v.stop()
+		}
+	}
+}
+
 // Resets all the globals used modified in tests.
 // Resetting ensures that the changes made to globals by one test doesn't affect others.
 func resetTestGlobals() {
@@ -518,6 +529,8 @@ func resetTestGlobals() {
 	resetGlobalIsEnvs()
 	// Reset global storage class flags
 	resetGlobalStorageEnvs()
+	// Reset global heal state
+	resetGlobalHealState()
 }
 
 // Configure the server for the test run.