Store eggdrop PID files to /var/run/<bot account>

Summary:
e.g. /var/run/viperserv/daeghrefn.pid

Fixes T1320.

Test Plan:

$ putdebug $env(HOME)/[string tolower $username].pid
[DEBUG] /var/run/viperserv/daeghrefn.pid

+ run state on Ysul

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1320

Differential Revision: https://devcentral.nasqueron.org/D1235