Removes logrus package and refactors logging messages (#5293)

This fix removes logrus package dependency and refactors the console
logging as the only logging mechanism by removing file logging support.
It rearranges the log message format and adds stack trace information
whenever trace information is not available in the error structure.
It also adds `--json` flag support for server logging.
When minio server is started with `--json` flag, all log messages are
displayed in json format, with no start-up and informational log
messages.
Fixes #5265 #5220 #5197

cmd/namespace-lock_test.go

@@ -21,6 +21,22 @@ import (
 	"time"
 )
 
+// WARNING:
+//
+// Expected source line number is hard coded, 32, in the
+// following test. Adding new code before this test or changing its
+// position will cause the line number to change and the test to FAIL
+// Tests getSource().
+func TestGetSource(t *testing.T) {
+	currentSource := func() string { return getSource() }
+	gotSource := currentSource()
+	// Hard coded line number, 32, in the "expectedSource" value
+	expectedSource := "[namespace-lock_test.go:32:TestGetSource()]"
+	if gotSource != expectedSource {
+		t.Errorf("expected : %s, got : %s", expectedSource, gotSource)
+	}
+}
+
 // Tests functionality provided by namespace lock.
 func TestNamespaceLockTest(t *testing.T) {
 	// List of test cases.