Raise incurred exception if appropriate

While fetching eventlog, if a communication problem
occurs, the exception was ignored and code fell through
to unitialized variable.  Fix this by raising if not the
value known to be ignored.

Change-Id: I7785d0b3695abd84a8cac23059c031956877db58

pyghmi/ipmi/events.py

@@ -515,6 +515,8 @@ class EventHandler(object):
             except pygexc.IpmiException as pi:
                 if pi.ipmicode == 203:
                     break
+                else:
+                    raise
             curr = struct.unpack_from('<H', buffer(rsp['data'][:2]))[0]
             targetlist.append(self._sel_decode(rsp['data'][2:]))
         return endat