pkg/log: reset the buffer in the tests (#2828)

Reset the buf otherwise we're not checking the new value.
Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/pkg/log/log_test.go

@@ -16,6 +16,7 @@ func TestDebug(t *testing.T) {
 	if x := f.String(); x != "" {
 		t.Errorf("Expected no debug logs, got %s", x)
 	}
+	f.Reset()
 
 	D = true
 	Debug("debug")
@@ -34,6 +35,7 @@ func TestDebugx(t *testing.T) {
 	if x := f.String(); !strings.Contains(x, debug+"debug") {
 		t.Errorf("Expected debug log to be %s, got %s", debug+"debug", x)
 	}
+	f.Reset()
 
 	Debug("debug")
 	if x := f.String(); !strings.Contains(x, debug+"debug") {
@@ -50,10 +52,12 @@ func TestLevels(t *testing.T) {
 	if x := f.String(); !strings.Contains(x, info+ts) {
 		t.Errorf("Expected log to be %s, got %s", info+ts, x)
 	}
+	f.Reset()
 	Warning(ts)
 	if x := f.String(); !strings.Contains(x, warning+ts) {
 		t.Errorf("Expected log to be %s, got %s", warning+ts, x)
 	}
+	f.Reset()
 	Error(ts)
 	if x := f.String(); !strings.Contains(x, err+ts) {
 		t.Errorf("Expected log to be %s, got %s", err+ts, x)