Fix chunk length when unicode on MCI

Unicode data probably won't work, but to the extent it could
work, it would be incorrect to do length on the unicode rather
than length of the utf-8 encoded data.

Change-Id: Id39484abff603fdaab421f3395063b17edd3ae15

pyghmi/ipmi/command.py

@@ -1011,8 +1011,9 @@ class Command(object):
         chunks = [data[i:i+15] for i in xrange(0, len(data), 15)]
         offset = 0
         for chunk in chunks:
+            chunk = bytearray(chunk, 'utf-8')
             cmddata = bytearray((0xdc, offset, len(chunk)))
-            cmddata += bytearray(chunk, 'utf-8')
+            cmddata += chunk
             self.xraw_command(netfn=0x2c, command=command, data=cmddata)
 
     def set_channel_access(self, channel=None,