[geary] Make GenericAccount::enumerate_folders_async debug PERIODIC as well.

[Michael Gratton <mjog src gnome org>]

commit c1a19dfa80b8be393392b44643f12c1736466ebb
Author: Michael James Gratton <mike vee net>
Date:   Tue Nov 21 10:41:06 2017 +1100

    Make GenericAccount::enumerate_folders_async debug PERIODIC as well.

 .../imap-engine/imap-engine-generic-account.vala   |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/src/engine/imap-engine/imap-engine-generic-account.vala 
b/src/engine/imap-engine/imap-engine-generic-account.vala
index 7eeabfc..2ac8e73 100644
--- a/src/engine/imap-engine/imap-engine-generic-account.vala
+++ b/src/engine/imap-engine/imap-engine-generic-account.vala
@@ -432,7 +432,11 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.Account {
         Cancellable? cancellable = this.enumerate_folder_cancellable = new Cancellable();
         this.refresh_folder_timer.reset();
 
-        debug("%s: Enumerating folders", to_string());
+        Logging.debug(
+            Logging.Flag.PERIODIC,
+            "%s: Enumerating folders",
+            to_string()
+        );
 
         bool successful = false;
         try {