Add command_prefix field to puppet mcagent

This will allow to run puppet with environment variables.
E.g. FACTER_foo=bar puppet apply ...

Change-Id: I1e435262e810ead46689078513607f6a99a19043
Implements: blueprint get-rid-cobbler-dnsmasq

mcagents/puppetd.ddl

@@ -97,6 +97,14 @@ action "runonce", :description => "Invoke a single puppet run" do
           :default     => true,
           :optional    => true
 
+    input :command_prefix,
+          :prompt      => "Puppet command prefix (allows to run puppet with variables)",
+          :description => "Allows to run puppet with variables (e.g. FACTER_foo=bar)",
+          :type        => :string,
+          :validation  => :shellsafe,
+          :default     => '',
+          :optional    => true
+
     output :output,
            :description => "Output from puppet",
            :display_as => "Output"

mcagents/puppetd.rb

@@ -202,7 +202,9 @@ module MCollective
         cwd = request.fetch(:cwd, '/')
         manifest =  request.fetch(:manifest, '/etc/puppet/manifests/site.pp')
         module_path = request.fetch(:modules, '/etc/puppet/modules')
+        command_prefix = request.fetch(:command_prefix, '')
         cmd = [
+          command_prefix,
           @puppetd,
           "-c #{cwd}",
           @puppetd_agent,