Change method of unplugging pif

When disallow-unplug of PIF config is true, it will fail.
Now ACKy changes setting if it is true before unplug a pif.
Merge pull request #69 from bpwook/logrotate_fix

Fix logrotate issue.
Merge pull request #71 from bpwook/pif-unplug

Change method of unplugging pif
Fix a bug

When log is being refreshed to run logrotate, existing handlers were
not cleared properly.