Moved to unless from if not to improve code clarity.  Changed wording of few error messages.
Moved to unless from if not to improve code clarity.  Changed
wording of few error messages.

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

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