Fix messages with new_size variables in logical_volume/lvm.rb
Fix Issue 14718 and 17920

Code as provided by Sander Hollaar in http://projects.puppetlabs.com/issues/14718
Problem is also described in http://projects.puppetlabs.com/issues/17920
Fix failed tests
Merge pull request #27 from raphink/messages

Fix messages with new_size variables in logical_volume/lvm.rb
Merge pull request #28 from raskas/master

Feature/14718: size 'undef' doesn't work when creating a new logical volume