Fix timeouts in PostgresNode::psql

Newer Perl or IPC::Run versions default to appending the filename to string
exceptions, e.g. the exception

    psql timed out

 is thrown as

    psql timed out at /usr/share/perl5/vendor_perl/IPC/Run.pm line 2961.

To handle this, match exceptions with !~ rather than ne.

From: Craig Ringer <craig@2ndquadrant.com>
Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>

src/test/perl/PostgresNode.pm

@@ -1139,7 +1139,7 @@ sub psql
 			# IPC::Run::run threw an exception. re-throw unless it's a
 			# timeout, which we'll handle by testing is_expired
 			die $exc_save
-			  if (blessed($exc_save) || $exc_save ne $timeout_exception);
+			  if (blessed($exc_save) || $exc_save !~ /^\Q$timeout_exception\E/);
 
 			$ret = undef;