Pass ssh command for port forwarding using array (#1469)

Switch to the command as an array format when passing the port
forwarding ssh command to spawn to switch to execution of the ssh
process directly instead of being executed by the default shell.

Fixes: #1467

lib/vagrant-libvirt/action/forward_ports.rb

@@ -87,12 +87,13 @@ module VagrantPlugins
                           gateway_ports)
           ssh_info = machine.ssh_info
           params = %W(
+            -n
             -L
             #{host_ip}:#{host_port}:#{guest_ip}:#{guest_port}
             -N
             #{ssh_info[:host]}
-          ).join(' ')
-          params += ' -g' if gateway_ports
+          )
+          params += '-g' if gateway_ports
 
           options = (%W(
             User=#{ssh_info[:username]}
@@ -105,32 +106,32 @@ module VagrantPlugins
             ForwardX11=#{ssh_info[:forward_x11] ? 'yes' : 'no'}
             IdentitiesOnly=#{ssh_info[:keys_only] ? 'yes' : 'no'}
           ) + ssh_info[:private_key_path].map do |pk|
-                "IdentityFile='\"#{pk}\"'"
-              end).map { |s| "-o #{s}" }.join(' ')
+                "IdentityFile=\"#{pk}\""
+              end
+          ).map { |s| ['-o', s] }.flatten
 
-          options += " -o ProxyCommand=\"#{ssh_info[:proxy_command]}\"" if machine.provider_config.proxy_command
+          options += ['-o', "ProxyCommand=\"#{ssh_info[:proxy_command]}\""] if machine.provider_config.proxy_command
+
+          ssh_cmd = ['ssh'] + options + params
 
           # TODO: instead of this, try and lock and get the stdin from spawn...
-          ssh_cmd = ''
           if host_port <= 1024
             @@lock.synchronize do
               # TODO: add i18n
               env[:ui].info 'Requesting sudo for host port(s) <= 1024'
               r = system('sudo -v')
               if r
-                ssh_cmd += 'sudo ' # add sudo prefix
+                ssh_cmd.unshift('sudo') # add sudo prefix
               end
             end
           end
 
-          ssh_cmd += "ssh -n #{options} #{params}"
-
-          @logger.debug "Forwarding port with `#{ssh_cmd}`"
+          @logger.debug "Forwarding port with `#{ssh_cmd.join(' ')}`"
           log_file = ssh_forward_log_file(
             env[:machine], host_ip, host_port, guest_ip, guest_port,
           )
           @logger.info "Logging to #{log_file}"
-          spawn(ssh_cmd, [:out, :err] => [log_file, 'w'], :pgroup => true)
+          spawn(*ssh_cmd, [:out, :err] => [log_file, 'w'], :pgroup => true)
         end
 
         def ssh_forward_log_file(machine, host_ip, host_port, guest_ip, guest_port)