release: always assign name from server data

Prior to this change, if a user created a Release class by specifying an
ID number instead of a name string, the class would always set the name
property to None. For example, this would be None:

  Release(id=1234).name

Assign name when we process all the other data attributes in _setattr().

errata_tool/release.py

@@ -25,6 +25,7 @@ def _setattr(self):
         self.attributes = self.data['attributes']
         self.relationships = self.data['relationships']
         self.id = self.data['id']
+        self.name = self.attributes['name']
         self.program_manager = \
             self.relationships['program_manager']['login_name'] if \
             self.relationships.get('program_manager') else None