MFC r266553, r266554:

r266553:
  Add forward-compatibility glue with pkg-1.3:
   - Use ASSUME_ALWAYS_YES=YES instead of ASSUME_ALWAYS_YES=1
     since pkg-1.3 expects "yes" or "true" values.
   - Before exporting PKG_ABI, strip extra characters from what
     is parsed from 'pkg -vv'.  This causes problems further down
     when creating the packages directory for inclusion on the
     dvd1.iso.  Previously PKG_ABI would be 'freebsd:9:x86:64',
     but now is '"freebsd:9:x86:64";' in pkg-1.3.

r266554:
  Disable the main FreeBSD pkg(7) repositories in the dvd
  repository configuration to avoid fetching from upstream
  in case there may be conflicts.

Sponsored by:	The FreeBSD Foundation