Cleanly degrade on bad BMC time format

If a BMC provided a time, but the format was not compliant,
it caused an exception.  Now gracefully degrade to not
doing time correction if time cannot be parsed.

Change-Id: I5ab45d51913232016bb55d3595ea30188bbfe2e7

pyghmi/redfish/command.py

@@ -1028,6 +1028,7 @@ class Command(object):
         correction = timedelta(0)
         if currtime:
             currtime = _parse_time(currtime)
+        if currtime:
             now = datetime.now(tz.tzoffset('', 0))
             try:
                 correction = now - currtime