cel/cel_pgsql.c: Use the 'SEP' macro when appending a column name

When appending a column name to the sql buffer, the predicate, "if first is
non-null, use empty string; else, use comma", is identical to the 'SEP' macro
definition. Since they are the same, this patch replaces the redundant
predicate statement with the 'SEP' macro.

Change-Id: Ib8b6138b06a48381723108a05ab8752cb8700509

cel/cel_pgsql.c

@@ -201,7 +201,7 @@ static void pgsql_log(struct ast_event *event)
 		AST_RWLIST_RDLOCK(&psql_columns);
 		AST_RWLIST_TRAVERSE(&psql_columns, cur, list) {
 			LENGTHEN_BUF1(strlen(cur->name) + 2);
-			ast_str_append(&sql, 0, "%s\"%s\"", first ? "" : ",", cur->name);
+			ast_str_append(&sql, 0, "%s\"%s\"", SEP, cur->name);
 
 			if (strcmp(cur->name, "eventtime") == 0) {
 				if (strncmp(cur->type, "int", 3) == 0) {