Errno:EPERM on vagrant halt

[jchook]

Ubuntu 16.04
VirtualBox 5.2
Vagrant 2.0.3
vagrant-notify-forwarder 0.5.0

Getting this error when attempting a graceful shutdown:

`kill': Operation not permitted (Errno::EPERM)

The issue seems to be in this file: vagrant-notify-forwarder-0.5.0/lib/vagrant-notify-forwarder/action/stop_host_forwarder.rb:23

If I add rescue Errno::EPERM, the problem is "fixed".

Seems like maybe an old PID was stored due to non-graceful shutdown of the VM yesterday.

[jchook]

Hey just an update. This bug still affects me and requires periodic patching.