Add {last_virtual_fail_count} for execute alerter
Add {last_virtual_fail_count} for execute alerter

{virtual_fail_count} is 0 after a success, so it can't be used to say
how many times the monitor failed before it just succeeded.

Fixes #69

jamesoff/simplemonitor,jamesoff/simplemonitor,jamesoff/simplemonitor,jamesoff/simplemonitor,jamesoff/simplemonitor