Fixes bug where WORKERS was sometimes being sent to "NAN"

For the case where  "ansible_processor_cores": "NA"  and
facter_processorcount wasn't the WORKERS was set to the string "NA" *
the multiplier (like batman).
This will try to convert both to numbers and if the conversion fails it
will fall through and just set the WORKERS to the multiplier.
Merge pull request #158 from edx/jarv/fix-processor-facts

Fixes bug where WORKERS was sometimes being set to "NAN"