power_spec.rb: work with latest puppetlabs-apache

Modulefile no longer exists in puppetlabs-apache, check metadata.json
instead.

Signed-off-by: Scott Garman <sgarman@zenlinux.com>
Merge pull request #310 from ScottGarman/master

power_spec.rb: work with latest puppetlabs-apache

Thank you,@ScottGarman.