Fixup on emulator_path configuration.

Thanks to Gerben Meijer for the fix!

lib/vagrant-libvirt/action/create_domain.rb

@@ -45,6 +45,7 @@ module VagrantPlugins
           @domain_volume_cache = config.volume_cache
           @kernel = config.kernel
           @cmd_line = config.cmd_line
+          @emulator_path = config.emulator_path
           @initrd = config.initrd
           @graphics_type = config.graphics_type
           @graphics_autoport = config.graphics_autoport

lib/vagrant-libvirt/config.rb

@@ -444,6 +444,7 @@ module VagrantPlugins
         @tpm_type = 'passthrough' if @tpm_type == UNSET_VALUE
         @tpm_path = nil if @tpm_path == UNSET_VALUE
         @nic_adapter_count = 8 if @nic_adapter_count == UNSET_VALUE
+        @emulator_path = nil if @emulator_path == UNSET_VALUE
 
         # Boot order
         @boot_order = [] if @boot_order == UNSET_VALUE