tests: Add context cancelation (#15374)

A huge number of goroutines would build up from various monitors

When creating test filesystems provide a context so they can shut down when no longer needed.

cmd/config-current_test.go

@@ -26,7 +26,10 @@ import (
 )
 
 func TestServerConfig(t *testing.T) {
-	objLayer, fsDir, err := prepareFS()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	objLayer, fsDir, err := prepareFS(ctx)
 	if err != nil {
 		t.Fatal(err)
 	}