Removed the use of ccmHistoryRunningLastSaved checking for cisco configs.
This value updated to the current time e.g. on the command 'sh run' and thus
there's no value in checking this OID (as far as I can see.)
Now only produces a warning/critical if the current running config is ahead of
the startup config for more than X minutes.
Also fixed the mitigation parameter. Using this parameter didn't have any effect
on the outcome of the check.