Moved to unless from if not to improve code clarity.  Added TODO for future reference.  Changed wording of few error messages.
Moved to unless from if not to improve code clarity.  Added TODO
for future reference.  Changed wording of few error messages.

Signed-off-by: Krzysztof Wilczynski <9bf091559fc98493329f7d619638c79e91ccf029@linux.com>

fuel-infra/puppetlabs-stdlib,HelenCampbell/puppetlabs-stdlib,yadavnikhil/puppetlabs-stdlib,puppetlabs/puppetlabs-stdlib,jbondpdx/puppetlabs-stdlib,DavidS/puppetlabs-stdlib