Add support for pbzip2 -d -c instead of bzcat using base_packages.has_pbzip2()

pbzip2 decompress only speeds up if pbzip2 was used to compress, but
still this saves some time.

Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
Merge pull request #857 from rbbratta/pbzip2

Add support for pbzip2 -d -c instead of bzcat using base_packages.has_pb...