Replace Chinese punctuation with English punctuation

Curly quotes(Chinese punctuation) usually input from Chinese input method.
When read from english context, it makes some confusion.

Change-Id: Ibca2c0a6236de383097267272f151f30aa4afe74

api-ref/source/v1/parameters.yaml

@@ -732,7 +732,7 @@ server_name:
   type: string
 server_power_state:
   description: |
-    The current power state of this server. Usually, “power on” or “power off”, but may be “None”
+    The current power state of this server. Usually, "power on" or "power off", but may be "None"
     if Mogan is unable to determine the power state (eg, due to hardware failure)
   in: body
   required: true