Fix MySQL DSN -> tags parsing

Closes #297

plugins/mysql/mysql_test.go

@@ -81,3 +81,62 @@ func TestMysqlDefaultsToLocal(t *testing.T) {
 
 	assert.True(t, len(acc.Points) > 0)
 }
+
+func TestMysqlParseDSN(t *testing.T) {
+	tests := []struct {
+		input  string
+		output string
+	}{
+		{
+			"",
+			"127.0.0.1:3306",
+		},
+		{
+			"localhost",
+			"127.0.0.1:3306",
+		},
+		{
+			"127.0.0.1",
+			"127.0.0.1:3306",
+		},
+		{
+			"tcp(192.168.1.1:3306)/",
+			"192.168.1.1:3306",
+		},
+		{
+			"tcp(localhost)/",
+			"localhost",
+		},
+		{
+			"root:passwd@tcp(192.168.1.1:3306)/?tls=false",
+			"192.168.1.1:3306",
+		},
+		{
+			"root@tcp(127.0.0.1:3306)/?tls=false",
+			"127.0.0.1:3306",
+		},
+		{
+			"root:passwd@tcp(localhost:3036)/dbname?allowOldPasswords=1",
+			"localhost:3036",
+		},
+		{
+			"root:foo@bar@tcp(192.1.1.1:3306)/?tls=false",
+			"192.1.1.1:3306",
+		},
+		{
+			"root:f00@b4r@tcp(192.1.1.1:3306)/?tls=false",
+			"192.1.1.1:3306",
+		},
+		{
+			"root:fl!p11@tcp(192.1.1.1:3306)/?tls=false",
+			"192.1.1.1:3306",
+		},
+	}
+
+	for _, test := range tests {
+		output, _ := parseDSN(test.input)
+		if output != test.output {
+			t.Errorf("Expected %s, got %s\n", test.output, output)
+		}
+	}
+}