Fix --disable_metrics parsing to accept empty string as input.

Signed-off-by: Vishnu kannan <vishnuk@google.com>

cadvisor.go

@@ -76,6 +76,10 @@ func (ml *metricSetValue) String() string {
 }
 
 func (ml *metricSetValue) Set(value string) error {
+	ignoreMetrics = metricSetValue{}
+	if value == "" {
+		return nil
+	}
 	for _, metric := range strings.Split(value, ",") {
 		if ignoreWhitelist.Has(container.MetricKind(metric)) {
 			(*ml).Add(container.MetricKind(metric))

cadvisor_test.go

@@ -27,3 +27,9 @@ func TestTcpMetricsAreDisabledByDefault(t *testing.T) {
 	flag.Parse()
 	assert.True(t, ignoreMetrics.Has(container.NetworkTcpUsageMetrics))
 }
+
+func TestTcpMetricsAreEnabledOnDemand(t *testing.T) {
+	assert.True(t, ignoreMetrics.Has(container.NetworkTcpUsageMetrics))
+	ignoreMetrics.Set("")
+	assert.False(t, ignoreMetrics.Has(container.NetworkTcpUsageMetrics))
+}