PostgresNode: initialize $timed_out if passed

Corrects an oversight in 2c83f435a3 where the $timed_out reference var
isn't initialized; using it would require the caller to initialize it
beforehand, which is cumbersome.

Author: Craig Ringer

src/test/perl/PostgresNode.pm

@@ -1032,6 +1032,8 @@ sub psql
 	  IPC::Run::timeout($params{timeout}, exception => $timeout_exception)
 	  if (defined($params{timeout}));
 
+	${$params{timed_out}} = 0 if defined $params{timed_out};
+
 	# IPC::Run would otherwise append to existing contents:
 	$$stdout = "" if ref($stdout);
 	$$stderr = "" if ref($stderr);