Tests: Add some PHP tests for 403 and 404 error handling.

Since the previous commit, we now properly handle 403 Forbidden & 404
Not Found errors in the PHP language module.

This adds a test for 403 Forbidden to test/test_php_application.py, but
also fixes a test in test/test_php_targets.py where we were checking for
503 but should have been a 404, which we now do.

Acked-by: Alejandro Colomar <alx@nginx.com>
Cc: Andrei Zeliankou <zelenkov@nginx.com>
[ Incorporates a couple of small test cleanups from Andrei ]
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

test/test_php_targets.py

@@ -45,7 +45,7 @@ class TestPHPTargets(TestApplicationPHP):
 
         assert self.get(url='/1')['body'] == '1'
         assert self.get(url='/2')['body'] == '2'
-        assert self.get(url='/blah')['status'] == 503  # TODO 404
+        assert self.get(url='/blah')['status'] == 404
         assert self.get(url='/')['body'] == 'index'
         assert self.get(url='/1.php?test=test.php/')['body'] == '1'