[Python] Fix two pylint warnings in swift-bench.py

Prior to this commit:

```
$ pylint utils/swift-bench.py 2>&1 | grep '(no-member)'
E:360,12: Instance of 'Test' has no 'results' member (no-member)
E:364,18: Instance of 'Test' has no 'output' member (no-member)
$
```

After this commit:

```
$ pylint utils/swift-bench.py 2>&1 | grep '(no-member)'
$
```

Author: practicalswift

utils/swift-bench.py

@@ -352,12 +352,15 @@ def __init__(self, name, source, processed_source, binary):
         self.processed_source = processed_source
         self.binary = binary
         self.status = ""
+        self.results = None
+        self.output = None
 
     def do_print(self):
         print("NAME: %s" % self.name)
         print("SOURCE: %s" % self.source)
         if self.status == "":
-            self.results.do_print()
+            if self.results is not None:
+                self.results.do_print()
         else:
             print("STATUS: %s" % self.status)
             print("OUTPUT:")