config: fix parsing of file permissions

The file permissions can be specified (unfortunately) as a string or an
octal integer. During the normalization step, every field is
unmarshalled into an interface{}. String types are kept in tact but
integers are converted to decimal integers. If the raw config
represented the permissions as an octal, it would be converted to
decimal _before_ it was saved to RawFilePermissions. Permissions() would
then try to convert it again, assuming it was an octal. The new behavior
doesn't assume the radix of the number, allowing decimal and octal
input.

config/config_test.go

@@ -276,6 +276,40 @@ Address=10.209.171.177/19
 	if cfg.Coreos.Update.RebootStrategy != "reboot" {
 		t.Errorf("Failed to parse locksmith strategy")
 	}
+
+	contents = `
+coreos:
+write_files:
+  - path: /home/me/notes
+    permissions: 0744
+`
+	cfg, err = NewCloudConfig(contents)
+	if err != nil {
+		t.Fatalf("Encountered unexpected error :%v", err)
+	}
+
+	if len(cfg.WriteFiles) != 1 {
+		t.Error("Failed to parse correct number of write_files")
+	} else {
+		wf := cfg.WriteFiles[0]
+		if wf.Content != "" {
+			t.Errorf("WriteFile has incorrect contents '%s'", wf.Content)
+		}
+		if wf.Encoding != "" {
+			t.Errorf("WriteFile has incorrect encoding %s", wf.Encoding)
+		}
+		// Verify that the normalization of the config converted 0744 to its decimal
+		// representation, 484.
+		if wf.RawFilePermissions != "484" {
+			t.Errorf("WriteFile has incorrect permissions %s", wf.RawFilePermissions)
+		}
+		if wf.Path != "/home/me/notes" {
+			t.Errorf("WriteFile has incorrect path %s", wf.Path)
+		}
+		if wf.Owner != "" {
+			t.Errorf("WriteFile has incorrect owner %s", wf.Owner)
+		}
+	}
 }
 
 // Assert that our interface conversion doesn't panic