Update some docker provider test

- Split the file into smaller ones (docker, swarm and service tests)
- Use some builder to reduce a little bit the noise for creating containers

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

provider/provider.go

@@ -51,6 +51,7 @@ func (p *BaseProvider) MatchConstraints(tags []string) (bool, *types.Constraint)
 	return true, nil
 }
 
+// GetConfiguration return the provider configuration using templating
 func (p *BaseProvider) GetConfiguration(defaultTemplateFile string, funcMap template.FuncMap, templateObjects interface{}) (*types.Configuration, error) {
 	var (
 		buf []byte
@@ -60,7 +61,7 @@ func (p *BaseProvider) GetConfiguration(defaultTemplateFile string, funcMap temp
 	var defaultFuncMap = template.FuncMap{
 		"replace":   replace,
 		"tolower":   strings.ToLower,
-		"Normalize": Normalize,
+		"normalize": Normalize,
 		"split":     split,
 		"contains":  contains,
 	}
@@ -112,6 +113,7 @@ func split(sep, s string) []string {
 	return strings.Split(s, sep)
 }
 
+// Normalize transform a string that work with the rest of traefik
 func Normalize(name string) string {
 	fargs := func(c rune) bool {
 		return !unicode.IsLetter(c) && !unicode.IsNumber(c)