MODULES-633 - Fix for ip6tables

If the packages for ip6tables aren't installed, the provider will throw
an exception. Fix the provider to check to make sure the variable exists
first, and update params.pp to include the required package for EL6.

lib/puppet/provider/firewall/ip6tables.rb

@@ -45,7 +45,8 @@
 
 
   def initialize(*args)
-    if Facter.fact('ip6tables_version').value.match /1\.3\.\d/
+    ip6tables_version = Facter.value('ip6tables_version')
+    if ip6tables_version and ip6tables_version.match /1\.3\.\d/
       raise ArgumentError, 'The ip6tables provider is not supported on version 1.3 of iptables'
     else
       super

manifests/params.pp

@@ -22,7 +22,7 @@
           if versioncmp($::operatingsystemrelease, '7.0') >= 0 {
             $package_name = 'iptables-services'
           } else {
-            $package_name = undef
+            $package_name = 'iptables-ipv6'
           }
           $service_name = 'iptables'
         }