(CFACT-125) Resolve architecture fact when passed as an argument

Prior to this commit, when running `cfacter architecture` the
architecture fact would not resolve, despite the fact that it
did resolve when `cfacter` was run without any arguments.

This commit updates the POSIX processors resolver constructor to
properly include the architecture fact so it can be resolved by itself.
Merge pull request #140 from whopper/cfact-125/arch-resolution-fix

(CFACT-125) Resolve architecture fact when passed as an argument
(CFACT-104) fix segv for dmi facts solaris

Previously, dmi facts relied on the architecture fact being resolved, and
was using the value without checking whether it was resolved or not. This
resulted in core dumps when the fact was not resolved.

This patch incorporates a null check to make sure that it does not core
dump.