Fix deprecation warnings

[KrzysztofHajdamowicz]

Warning: This method is deprecated, please use match expressions with Stdlib::Compat::String instead. They are described at https://docs.puppet.com/puppet/latest/reference/lang_data_type.html#match-expressions. at ["/etc/puppetlabs/code/environments/production/modules/dnsmasq/manifests/service.pp", 5]:["/etc/puppetlabs/code/environments/production/modules/profile/manifests/dnsmasq.pp", 2]
   (location: /etc/puppetlabs/code/environments/production/modules/stdlib/lib/puppet/functions/deprecation.rb:28:in `deprecation')

Seen on Puppet 5.5.16, tested on 5.5 and 6.x

[ashish1099]

@saz can we please get this PR merged :)