Ignore boolean keys in my.cnf. (#283)

Below is valid MySQL config however mysqld_exporter fails to read it,
because of the boolean keys.
Config:
```
[client]
user = root
password = abc123

[mysql]
skip-auto-rehash
```

Signed-off-by: Kamil Dziedzic <[email protected]>

Author: arvenil

mysqld_exporter.go

@@ -65,7 +65,11 @@ var scrapers = map[collector.Scraper]bool{
 
 func parseMycnf(config interface{}) (string, error) {
 	var dsn string
-	cfg, err := ini.Load(config)
+	opts := ini.LoadOptions{
+		// MySQL ini file can have boolean keys.
+		AllowBooleanKeys: true,
+	}
+	cfg, err := ini.LoadSources(opts, config)
 	if err != nil {
 		return dsn, fmt.Errorf("failed reading ini file: %s", err)
 	}

mysqld_exporter_test.go

@@ -54,6 +54,14 @@ func TestParseMycnf(t *testing.T) {
 			host = 1.2.3.4
 			port = 3307
 		`
+		ignoreBooleanKeys = `
+			[client]
+			user = root
+			password = abc123
+
+			[mysql]
+			skip-auto-rehash
+		`
 		badConfig = `
 			[client]
 			user = root
@@ -67,10 +75,7 @@ func TestParseMycnf(t *testing.T) {
 			[hello]
 			world = ismine
 		`
-		badConfig4 = `
-			[hello]
-			world
-		`
+		badConfig4 = `[hello`
 	)
 	convey.Convey("Various .my.cnf configurations", t, func() {
 		convey.Convey("Local tcp connection", func() {
@@ -93,21 +98,25 @@ func TestParseMycnf(t *testing.T) {
 			dsn, _ := parseMycnf([]byte(remoteConfig))
 			convey.So(dsn, convey.ShouldEqual, "dude:nopassword@tcp(1.2.3.4:3307)/")
 		})
+		convey.Convey("Ignore boolean keys", func() {
+			dsn, _ := parseMycnf([]byte(ignoreBooleanKeys))
+			convey.So(dsn, convey.ShouldEqual, "root:abc123@tcp(localhost:3306)/")
+		})
 		convey.Convey("Missed user", func() {
 			_, err := parseMycnf([]byte(badConfig))
-			convey.So(err, convey.ShouldNotBeNil)
+			convey.So(err, convey.ShouldBeError, fmt.Errorf("no user or password specified under [client] in %s", badConfig))
 		})
 		convey.Convey("Missed password", func() {
 			_, err := parseMycnf([]byte(badConfig2))
-			convey.So(err, convey.ShouldNotBeNil)
+			convey.So(err, convey.ShouldBeError, fmt.Errorf("no user or password specified under [client] in %s", badConfig2))
 		})
 		convey.Convey("No [client] section", func() {
 			_, err := parseMycnf([]byte(badConfig3))
-			convey.So(err, convey.ShouldNotBeNil)
+			convey.So(err, convey.ShouldBeError, fmt.Errorf("no user or password specified under [client] in %s", badConfig3))
 		})
 		convey.Convey("Invalid config", func() {
 			_, err := parseMycnf([]byte(badConfig4))
-			convey.So(err, convey.ShouldNotBeNil)
+			convey.So(err, convey.ShouldBeError, fmt.Errorf("failed reading ini file: unclosed section: %s", badConfig4))
 		})
 	})
 }