Fix for problems found by @dguerri

* TLSConfig['verify'] has to be set to False if we're only encrypting the
  connection, not verifying the host.
* tls_hostname was not set if tls_ca_cert was not present

https://github.com/ansible/ansible-modules-core/pull/926#issuecomment-78573877

lib/ansible/modules/cloud/docker/docker.py

@@ -571,7 +571,6 @@ class DockerManager(object):
         if not tls_ca_cert and env_cert_path:
             tls_ca_cert = os.path.join(env_cert_path, 'ca.pem')
 
-        if tls_ca_cert:
         tls_hostname = module.params.get('tls_hostname')
         if tls_hostname is None:
             if env_docker_hostname:
@@ -614,8 +613,10 @@ class DockerManager(object):
                 else:
                     params['verify'] = True
                     params['assert_hostname'] = tls_hostname
+            elif use_tls == 'encrpyt':
+                params['verify'] = False
 
-            if params or use_tls == 'encrypt':
+            if params:
                 # See https://github.com/docker/docker-py/blob/d39da11/docker/utils/utils.py#L279-L296
                 docker_url = docker_url.replace('tcp://', 'https://')
                 tls_config = docker.tls.TLSConfig(**params)