Start callhome immediately after enabling (#19764)

Currently, on enabling callhome (or restarting the server), the callhome
job gets scheduled. This means that one has to wait for 24hrs (the
default frequency duration) to see it in action and to figure out if it
is working as expected.

It will be a better user experience to perform the first callhome
execution immediately after enabling it (or on server start if already
enabled).

Also, generate audit event on callhome execution, setting the error
field in case the execution has failed.

cmd/callhome.go

@@ -80,6 +80,9 @@ func runCallhome(ctx context.Context, objAPI ObjectLayer) bool {
 	ctx = lkctx.Context()
 	defer locker.Unlock(lkctx)
 
+	// Perform callhome once and then keep running it at regular intervals.
+	performCallhome(ctx)
+
 	callhomeTimer := time.NewTimer(globalCallhomeConfig.FrequencyDur())
 	defer callhomeTimer.Stop()
 
@@ -141,11 +144,14 @@ func performCallhome(ctx context.Context) {
 		select {
 		case hi, hasMore := <-healthInfoCh:
 			if !hasMore {
+				auditOptions := AuditLogOptions{Event: "callhome:diagnostics"}
 				// Received all data. Send to SUBNET and return
 				err := sendHealthInfo(ctx, healthInfo)
 				if err != nil {
 					internalLogIf(ctx, fmt.Errorf("Unable to perform callhome: %w", err))
+					auditOptions.Error = err.Error()
 				}
+				auditLogInternal(ctx, auditOptions)
 				return
 			}
 			healthInfo = hi