Fix display of host details when cpu_info is empty

If a Blazar host was created with an empty cpu_info value, displaying
host details would fail with the error:

    SyntaxError: unexpected EOF while parsing (<string>, line 0)

This is because calling eval() on an empty string raises a SyntaxError.
This patch ensures that if cpu_info is empty, it is set to an empty
dictionary instead.

Change-Id: I38d9f92fd7937de4ec1492d06ddea834b6c423ef

blazar_dashboard/api/client.py

@@ -51,7 +51,10 @@ class Host(base.APIDictWrapper):
         super(Host, self).__init__(apiresource)
 
     def cpu_info_dict(self):
-        return eval(getattr(self, 'cpu_info', ""))
+        cpu_info_dict = getattr(self, 'cpu_info', '{}')
+        if not cpu_info_dict:
+            cpu_info_dict = '{}'
+        return eval(cpu_info_dict)
 
     def extra_capabilities(self):
         excaps = {}