pkg/51627: Change default PKG_DBDIR on OpenBSD

[luiz.de.milon%gmail.com@localhost]

>Number:         51627
>Category:       pkg
>Synopsis:       Change default PKG_DBDIR on OpenBSD
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Nov 13 20:20:00 +0000 2016
>Originator:     Luiz de Milon
>Release:        pkgsrc-2016Q3
>Organization:
Arrowheads
>Environment:
OpenBSD ayakashi 6.0 GENERIC.MP#2319 amd64

>Description:
OpenBSD uses /var/db/pkg for its package database by default, so pkgsrc should default to something else.
>How-To-Repeat:
Bootstrap pkgsrc with default options, the mk.conf will say PKG_DBDIR is /var/db/pkg.
>Fix:
Change default PKG_DBDIR on OpenBSD to /var/pkgdb or similar.