image-fuzzer: Use %r for all fiels at Field.__repr__()

This makes the formatting code simpler, and safer if we change
the type of self.value from str to bytes.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20191016192430.25098-6-ehabkost@redhat.com
Message-Id: <20191016192430.25098-6-ehabkost@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

tests/image-fuzzer/qcow2/layout.py

@@ -53,8 +53,8 @@ def __iter__(self):
         return iter([self.fmt, self.offset, self.value, self.name])
 
     def __repr__(self):
-        return "Field(fmt='%s', offset=%d, value=%s, name=%s)" % \
-            (self.fmt, self.offset, str(self.value), self.name)
+        return "Field(fmt=%r, offset=%r, value=%r, name=%r)" % \
+            (self.fmt, self.offset, self.value, self.name)
 
 
 class FieldsList(object):