Use a regular command instead of the puppet() command

In the switch from beaker-puppet to beaker_puppet_helpers this was
removed. Now it uses a regular shell command to achieve the same.

spec/acceptance/puppet_spec.rb

@@ -2,7 +2,7 @@
 
 describe 'Scenario: install puppet' do
   before(:context) do
-    on default, puppet('resource', 'service', 'puppet', 'ensure=stopped', 'enable=false')
+    on default, 'puppet resource service puppet ensure=stopped enable=false'
   end
 
   it_behaves_like 'an idempotent resource' do

spec/acceptance/puppetserver_latest_spec.rb

@@ -3,7 +3,7 @@
 describe 'Scenario: install puppetserver (latest):', unless: unsupported_puppetserver do
   before(:all) do
     if check_for_package(default, 'puppetserver')
-      on default, puppet('resource package puppetserver ensure=purged')
+      on default, 'puppet resource package puppetserver ensure=purged'
       on default, 'rm -rf /etc/sysconfig/puppetserver /etc/puppetlabs/puppetserver'
       on default, 'find /etc/puppetlabs/puppet/ssl/ -type f -delete'
     end

spec/acceptance/puppetserver_upgrade_spec.rb

@@ -3,7 +3,7 @@
 describe 'Scenario: minor version upgrade', unless: unsupported_puppetserver do
   before(:all) do
     if check_for_package(default, 'puppetserver')
-      on default, puppet('resource package puppetserver ensure=purged')
+      on default, 'puppet resource package puppetserver ensure=purged'
       on default, 'rm -rf /etc/sysconfig/puppetserver /etc/puppetlabs/puppetserver'
       on default, 'rm -rf /etc/puppetlabs/puppet/ssl'
     end