Fix a argument mismatch in elasticache

I think in this commit 720aeffca2

There was bug introduced where the ElastiCacheManager init method has
a number of positional arguments like so.

```py
    def __init__(self, module, name, engine, cache_engine_version, node_type,
                 num_nodes, cache_port, parameter_group, cache_subnet_group,
                 cache_security_groups, security_group_ids, zone, wait,
                 hard_modify, region, **aws_connect_kwargs):
```

But then later in the code the positional arguments are passed in
like this.

```py
    elasticache_manager = ElastiCacheManager(module, name, engine,
                                             cache_engine_version, node_type,
                                             num_nodes, cache_port,
                                             cache_subnet_group,
                                             cache_security_groups,
                                             security_group_ids, parameter_group, zone, wait,
                                             hard_modify, region, **aws_connect_kwargs)
```

If you count, you can see that cache_subnet_group, is being passed in
where the manager expects to see parameter_group.

cloud/amazon/elasticache.py

@@ -445,6 +445,7 @@ class ElastiCacheManager(object):
 
     def _refresh_data(self, cache_cluster_data=None):
         """Refresh data about this cache cluster"""
+
         if cache_cluster_data is None:
             try:
                 response = self.conn.describe_cache_clusters(cache_cluster_id=self.name,
@@ -542,9 +543,10 @@ def main():
     elasticache_manager = ElastiCacheManager(module, name, engine,
                                              cache_engine_version, node_type,
                                              num_nodes, cache_port,
+                                             parameter_group,
                                              cache_subnet_group,
                                              cache_security_groups,
-                                             security_group_ids, parameter_group, zone, wait,
+                                             security_group_ids, zone, wait,
                                              hard_modify, region, **aws_connect_kwargs)
 
     if state == 'present':