Reduce startup time for cdr_tds with large CDR tables.

Since we are just checking for table existence, add a WHERE clause that will
return no rows but will raise an error if the table doesn't exist.

(closes issue #17380)
Reported by: kkwong
Patches:
      issue17380-01.patch uploaded by seanbright (license 71)
Tested by: kkwong


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@269006 65c4cc65-6c06-0410-ace0-fbb531ad65f3

cdr/cdr_tds.c

@@ -477,7 +477,7 @@ static int mssql_connect(void)
 		goto connect_fail;
 	}
 
-	snprintf(query, sizeof(query), "SELECT 1 FROM %s", table);
+	snprintf(query, sizeof(query), "SELECT 1 FROM %s WHERE 1 = 0", table);
 #ifdef FREETDS_PRE_0_62
 	if ((tds_submit_query(tds, query) != TDS_SUCCEED) || (tds_process_simple_query(tds, &result_type) != TDS_SUCCEED || result_type != TDS_CMD_SUCCEED))
 #else