middleware/file: correctly parse the stanza (#658)

* middleware/file: correctly parse the stanza

Parsing the file stanza would give precedence to 'transfer' and ignore
other bits if it wasn't specified.

This change fixes the parsing. The actually external CNAME retrieval is
working fine (once the upstream is correctly parsed).

This wasn't caught in tests, because we lack a parsing test for this.

Fixes #657

* Add tests

middleware/secondary/setup.go

@@ -48,6 +48,7 @@ func secondaryParse(c *caddy.Controller) (file.Zones, error) {
 	names := []string{}
 	origins := []string{}
 	for c.Next() {
+
 		if c.Val() == "secondary" {
 			// secondary [origin]
 			origins = make([]string, len(c.ServerBlockKeys))
@@ -63,10 +64,18 @@ func secondaryParse(c *caddy.Controller) (file.Zones, error) {
 			}
 
 			for c.NextBlock() {
-				t, f, e := file.TransferParse(c, true)
-				if e != nil {
-					return file.Zones{}, e
+
+				t, f := []string{}, []string{}
+				var e error
+
+				switch c.Val() {
+				case "transfer":
+					t, _, e = file.TransferParse(c, true)
+					if e != nil {
+						return file.Zones{}, e
+					}
 				}
+
 				for _, origin := range origins {
 					if t != nil {
 						z[origin].TransferTo = append(z[origin].TransferTo, t...)