Trivial: Fixes serial console minor nits

Commit [1] suggested that reversed() should be used
instead of [::-1].

Commit [2] suggested that a comment should be added with
the expected pipe_path format.

[1] f554c3f777
[2] f98af85eb2

Change-Id: I29e87a665d6bbcfc2f3c0d635b2d0fe252f3229b

nova/tests/unit/virt/hyperv/test_serialconsoleops.py

@@ -93,14 +93,14 @@ class SerialConsoleOpsTestCase(test_base.HyperVBaseTestCase):
     @mock.patch("os.path.exists")
     def test_get_console_output_exception(self, fake_path_exists, fake_open):
         self._serialops._pathutils.get_vm_console_log_paths.return_value = [
-            mock.sentinel.log_path]
+            mock.sentinel.log_path_1, mock.sentinel.log_path_2]
         fake_open.side_effect = IOError
         fake_path_exists.return_value = True
 
         self.assertRaises(exception.ConsoleLogOutputException,
                           self._serialops.get_console_output,
                           mock.sentinel.instance_name)
-        fake_open.assert_called_once_with(mock.sentinel.log_path, 'rb')
+        fake_open.assert_called_once_with(mock.sentinel.log_path_2, 'rb')
 
     @mock.patch('os.path.exists')
     @mock.patch.object(serialconsoleops.SerialConsoleOps,

nova/virt/hyperv/serialconsolehandler.py

@@ -145,6 +145,8 @@ class SerialConsoleHandler(object):
         # as we can't use the serial port ElementName attribute because of
         # a Hyper-V bug.
         for pipe_path in serial_port_conns:
+            # expected pipe_path:
+            # '\\.\pipe\fc1bcc91-c7d3-4116-a210-0cd151e019cd_rw'
             port_type = pipe_path[-2:]
             if port_type in [constants.SERIAL_PORT_TYPE_RO,
                              constants.SERIAL_PORT_TYPE_RW]:

nova/virt/hyperv/serialconsoleops.py

@@ -93,7 +93,7 @@ class SerialConsoleOps(object):
         try:
             log = b''
             # Start with the oldest console log file.
-            for log_path in console_log_paths[::-1]:
+            for log_path in reversed(console_log_paths):
                 if os.path.exists(log_path):
                     with open(log_path, 'rb') as fp:
                         log += fp.read()