allow ansible_ssh_private_key_file to be templated (thanks to benno)

lib/ansible/runner/__init__.py

@@ -708,6 +708,8 @@ class Runner(object):
         actual_pass = inject.get('ansible_ssh_pass', self.remote_pass)
         actual_transport = inject.get('ansible_connection', self.transport)
         actual_private_key_file = inject.get('ansible_ssh_private_key_file', self.private_key_file)
+        # allow ansible_ssh_private_key_file to be templated
+        actual_private_key_file = template.template(self.basedir, actual_private_key_file, inject, fail_on_undefined=True)
         self.sudo_pass = inject.get('ansible_sudo_pass', self.sudo_pass)
         self.su = inject.get('ansible_su', self.su)
         self.su_pass = inject.get('ansible_su_pass', self.su_pass)