Do not insensitively load the DNFConf

Do direct string matching instead of insensitive string matching. The
insensitive load will break when someone tries to add something with
capital letters twice. For example, the following will be allowed when
it should not be:

mixer repo add QtPy url
mixer repo add QtPy url

Do a regular load so the string comparison with upper-case names will
work.

Signed-off-by: Matthew Johnson <matthew.johnson@intel.com>

builder/builder.go

@@ -1682,7 +1682,7 @@ func (b *Builder) AddRepo(repoInfo []string) error {
 		return err
 	}
 
-	DNFConf, err := ini.InsensitiveLoad(b.Config.Builder.DNFConf)
+	DNFConf, err := ini.Load(b.Config.Builder.DNFConf)
 	if err != nil {
 		return err
 	}