gitea: minor fix to the RC script

This sets the working directory to / before issuing commands to Gitea.
Fix from the pgsql script; it addresses the following issue when
managing Gitea:

  # /etc/rc.d/gitea restart
  Stopping gitea.
  sh: Cannot determine current working directory
  Starting gitea.
  sh: Cannot determine current working directory

(and then Gitea not starting again)

Bumps PKGREVISION.

During freeze, but leaf package AFAICT.

Tested on NetBSD/amd64.

(khorben)