Save a reference to the config.
This fixes the AttributeError we hit in today's rawhide:
https://kojipkgs.fedoraproject.org/mash/rawhide-20150430/logs/mash.log
The error looks like:
```
Traceback (most recent call last):
File "/usr/bin/mash", line 105, in <module>
main()
File "/usr/bin/mash", line 91, in main
rc = themash.doMultilib()
File "/usr/lib/python2.7/site-packages/mash/__init__.py", line 610, in doMultilib
pid = self.doDepSolveAndMultilib(arch, repocache)
File "/usr/lib/python2.7/site-packages/mash/__init__.py", line 561, in doDepSolveAndMultilib
elif do_multi and method.select(pkg):
File "/usr/lib/python2.7/site-packages/mash/multilib.py", line 189, in select
if po.name in self.config.multilib_devel_blacklist:
AttributeError: DevelMultilibMethod instance has no attribute 'config'
```
Signed-off-by: Ralph Bean <rbean@redhat.com>