Use $operatingsystemmajrelease instead of $lsbmajdistrelease

It seems that $lsbmajdistrelease is no longer a fact available in current puppet (3.4.2), at least on CentOS 6.5

This uses $operatingsystemmajrelease if it exists, or the other. 

Without this change you get the error
```
Error: undefined method `<' for :undef:Symbol at /tmp/vagrant-puppet-1/modules-0/memcached/manifests/instance.pp:19 on node xxx
Wrapped exception:
undefined method `<' for :undef:Symbol
Error: undefined method `<' for :undef:Symbol at /tmp/vagrant-puppet-1/modules-0/memcached/manifests/instance.pp:19 on node xxx
```