provisioners/shell: Fix shell provisioning when config.binary is set to false [GH-3712]

The `config` in use was the Shell provisioner config that does not expose
access to the VM configs.

References https://github.com/fgrehm/vagrant-lxc/issues/284

CHANGELOG.md

@@ -11,6 +11,8 @@ BUG FIXES:
 
   - core: Hostnames can be one character. [GH-3713]
   - core: Don't lock machines on SSH actions. [GH-3664]
+  - provisioners/shell: Fix shell provisioner config validation when the
+    `binary` option is set to false [GH-3712]
   - providers/docker: default proxy VM won't use HGFS [GH-3687]
   - providers/docker: fix container linking [GH-3719]
   - providers/docker: Port settings expose to host properly. [GH-3723]

plugins/provisioners/shell/provisioner.rb

@@ -154,7 +154,7 @@ module VagrantPlugins
 
         # Replace Windows line endings with Unix ones unless binary file
         # or we're running on Windows.
-        if !config.binary && config.vm.communicator != :winrm
+        if !config.binary && @machine.config.vm.communicator != :winrm
           script.gsub!(/\r\n?$/, "\n")
         end