Support fix in facter 2.2 to lsbmajdistrelease

Facter 2.2 fixed the meaning of lsbmajdistrelease under Ubuntu
(so that e.g. Ubuntu 14.04.1 has lsbmajdistrelease = 14.04 rather
than 14).

To accomodate this fix, this commit changes the version check
to use a slightly looser regex.
I think it would be useful to link to the bug in a comment to explain why we're testing this:
https://tickets.puppetlabs.com/browse/FACT-688