Fix test-kitchen net-scp-error (#736)

This commit report setting added to ansible-beats repo to fix the
transient Net::SCP::Error reported in ansible-beats and
ansible-elasticsearch during test-kitchen CI tests.

.kitchen.yml

@@ -2,6 +2,9 @@
 driver:
   name: docker
 
+transport:
+  max_ssh_sessions: 6
+
 provisioner:
   name: ansible_playbook
   hosts: localhost