proper test for blocking commands

Here my attempt to fix tests for blocking commands. I do not know why, but it is not possible to create other connection inside test:
```python
other_redis = yield from create_redis('localhost', self.redis_port, loop=self.loop)
```
results in:
```python
  File "tests/_testutil.py", line 18, in wrapper
    ret = loop.run_until_complete(fun(test, *args, **kw))
  File "/usr/lib/python3.4/asyncio/base_events.py", line 208, in run_until_complete
    return future.result()
  File "/usr/lib/python3.4/asyncio/futures.py", line 243, in result
    raise self._exception
  File "/usr/lib/python3.4/asyncio/tasks.py", line 321, in _step
    result = next(coro)
  File "tests/list_commands_test.py", line 30, in test_blpop
    other = yield from create_redis('localhost', self.redis_port, loop=self.loop)
  File "/home/nick/sources/python/aioredis/aioredis/commands/__init__.py", line 90, in create_redis
    conn = yield from create_connection(address, db, password, loop=loop)
  File "/home/nick/sources/python/aioredis/aioredis/connection.py", line 36, in create_connection
    address, loop=loop)
  File "/usr/lib/python3.4/asyncio/streams.py", line 114, in open_unix_connection
    lambda: protocol, path, **kwds)
  File "/usr/lib/python3.4/asyncio/unix_events.py", line 188, in create_unix_connection
    yield from self.sock_connect(sock, path)
  File "/usr/lib/python3.4/asyncio/futures.py", line 350, in __iter__
    return self.result()  # May raise too.
  File "/usr/lib/python3.4/asyncio/futures.py", line 243, in result
    raise self._exception
  File "/usr/lib/python3.4/asyncio/selector_events.py", line 295, in _sock_connect
    sock.connect(address)
FileNotFoundError: [Errno 2] No such file or directory
```
So I added new connection creation to ```setUp()``` and everithing works just fine.
Is this something with my ```redis```?