Comment 7 for bug 1571492

After some attempts to make it work without polling, I've had not much success, it still hangs sometimes. Maybe there is a locking problem in paramiko's buffered_pipe:

Traceback (most recent call last):
  File "tempest/test.py", line 113, in wrapper
    return f(self, *func_args, **func_kwargs)
  File "/opt/stack/ironic/ironic_tempest_plugin/tests/scenario/test_baremetal_basic_ops.py", line 124, in test_baremetal_server_ops
    self.verify_partition(vm_client, 'ephemeral0', '/mnt', eph_size)
  File "/opt/stack/ironic/ironic_tempest_plugin/tests/scenario/test_baremetal_basic_ops.py", line 87, in verify_partition
    num_bytes = client.exec_command(cmd).rstrip('\n')
  File "tempest/common/utils/linux/remote_client.py", line 44, in exec_command
    return self.ssh_client.exec_command(cmd)
  File "tempest/lib/common/ssh.py", line 145, in exec_command
    if channel.recv_ready():
  File "/usr/local/lib/python2.7/dist-packages/paramiko/channel.py", line 580, in recv_ready
    return self.in_buffer.read_ready()
  File "/usr/local/lib/python2.7/dist-packages/paramiko/buffered_pipe.py", line 105, in read_ready
    self._lock.acquire()