fix 223730, clear imap status messages when finished running imap urls, sr=mscott

mailnews/imap/src/nsImapMailFolder.cpp

@@ -4786,6 +4786,7 @@ nsImapMailFolder::OnStopRunningUrl(nsIURI *aUrl, nsresult aExitCode)
 
    if (imapUrl)
    {
+        DisplayStatusMsg(imapUrl, NS_LITERAL_STRING("").get());
         nsImapAction imapAction = nsIImapUrl::nsImapTest;
         imapUrl->GetImapAction(&imapAction);
         if (imapAction == nsIImapUrl::nsImapMsgFetch || imapAction == nsIImapUrl::nsImapMsgDownloadForOffline)