Minor clean-up follow-up to timeout on read() fix

Just some minor cleanup driven from the review process.

Change-Id: I0b3d73c251d6da6d85e11279990dcc36751e27e7

ironic_python_agent/extensions/standby.py

@@ -282,7 +282,6 @@ class ImageDownload(object):
                  any reason.
         """
         self._time = time_obj or time.time()
-        self._last_chunk_time = None
         self._image_info = image_info
         self._request = None
 
@@ -344,6 +343,7 @@ class ImageDownload(object):
         :returns: A chunk of the image. Size of chunk is IMAGE_CHUNK_SIZE
                   which is a constant in this module.
         """
+        self._last_chunk_time = None
         for chunk in self._request.iter_content(IMAGE_CHUNK_SIZE):
             # Per requests forum posts/discussions, iter_content should
             # periodically yield to the caller for the client to do things

ironic_python_agent/tests/unit/extensions/test_standby.py

@@ -1217,7 +1217,6 @@ class TestStandbyExtension(base.IronicAgentTest):
             status_code = 200
 
             def __init__(self, url, stream, proxies, verify, cert, timeout):
-                time.sleep(1)
                 self.count = 0
 
             def __iter__(self):
@@ -1227,12 +1226,8 @@ class TestStandbyExtension(base.IronicAgentTest):
                 if self.count == 1:
                     time.sleep(4)
                     return None
-                if self.count < 3:
-                    self.count += 1
-                    return "meow"
-                else:
-                    time.sleep(30)
-                    raise StopIteration
+                self.count += 1
+                return "meow"
 
             def iter_content(self, chunk_size):
                 return self