Replace calls to getmessagelist() to alternatives

getmessagelist() is slow for the mapped UID case, so replace some of its
occurences with calls that are optimized for this case, ie
getmessagecount() and uidexists().

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Reviewed-and-tested-by: Vincent Beffara <vbeffara@ens-lyon.fr>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/folder/Base.py

@@ -318,7 +318,7 @@ class BaseFolder:
             flags = self.getmessageflags(uid)
             rtime = self.getmessagetime(uid)
             
-            if uid in dstfolder.getmessagelist():
+            if dstfolder.uidexists(uid):
                 # dst has message with that UID already, only update status
                 statusfolder.savemessage(uid, None, flags, rtime)
                 return