daemon/config: group JSON preprocessing steps

Signed-off-by: Bjorn Neergaard <bneergaard@mirantis.com>

daemon/config/config.go

@@ -410,14 +410,14 @@ func getConflictFreeConfiguration(configFile string, flags *pflag.FlagSet) (*Con
 		return nil, err
 	}
 
-	var config Config
-
 	// Strip the UTF-8 BOM if present ([RFC 8259] allows JSON implementations to optionally strip the BOM for
 	// interoperability; do so here as Notepad on older versions of Windows Server insists on a BOM).
 	// [RFC 8259]: https://tools.ietf.org/html/rfc8259#section-8.1
 	b = bytes.TrimPrefix(b, []byte("\xef\xbb\xbf"))
-
+	// Trim whitespace so that an empty config can be detected for an early return.
 	b = bytes.TrimSpace(b)
+
+	var config Config
 	if len(b) == 0 {
 		return &config, nil // early return on empty config
 	}