Fix fallbackdata

Fallbackdata was actually being preferred rather than a
last resort.  Fix by changing to a more usual return
scheme.

Change-Id: I098dfc424c173c87c24a712efdebefb46f724473

pyghmi/ipmi/command.py

@@ -706,16 +706,15 @@ class Command(object):
         fallbackreadings = []
         try:
             self.oem_init()
-            self._oem.get_health(summary)
+            fallbackreadings = self._oem.get_health(summary)
             for reading in self.get_sensor_data():
                 if reading.health != const.Health.Ok:
                     summary['health'] |= reading.health
                     summary['badreadings'].append(reading)
         except exc.BypassGenericBehavior:
             pass
-        except exc.FallbackData as fd:
-            if not summary['badreadings']:
-                summary['badreadings'] = fd.fallbackdata
+        if not summary['badreadings']:
+            summary['badreadings'] = fallbackreadings
         return summary
 
     def get_sensor_reading(self, sensorname):

pyghmi/ipmi/oem/generic.py

@@ -302,7 +302,7 @@ class OEMHandler(object):
         :param summary: The health summary as prepared by the generic function
         :return: Nothing, modifies the summary object
         """
-        return
+        return []
 
     def set_hostname(self, hostname):
         """OEM specific hook to specify name information

pyghmi/ipmi/oem/lenovo/imm.py

@@ -1733,7 +1733,7 @@ class XCCClient(IMMClient):
                     'health': pygconst.Health.Warning,
                     'type': 'LED',
                 }, ''))
-        raise pygexc.FallbackData(fallbackdata)
+        return fallbackdata
         # Will use the generic handling for unhealthy systems
 
     def get_licenses(self):