core: AttributeError: 'SshConnection' object has no attribute '_client'

Home Assistant release with the issue: 0.100.2

Last working Home Assistant release (if known): N/K

Operating environment (Hass.io/Docker/Windows/etc.): Hassio

Integration: AsusWRT

Description of problem: Integration crashes and cause problems with device tracking.

Problem-relevant configuration.yaml entries and (fill out even if it seems unimportant):

asuswrt: 
  host: !secret asuswrt_host
  username: !secret asuswrt_username
  ssh_key: '/config/custom_components/asuswrt_ssh/asuswrt_ssh_key'
#  password: !secret asuswrt_password
  sensors: 
    - upload 
    - download 
    - upload_speed
    - download_speed

Traceback (if applicable):

Error doing job: Task exception was never retrieved
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/device_tracker/setup.py", line 164, in async_device_tracker_scan
    found_devices = await scanner.async_scan_devices()
  File "/usr/src/homeassistant/homeassistant/components/asuswrt/device_tracker.py", line 36, in async_scan_devices
    await self.async_update_info()
  File "/usr/src/homeassistant/homeassistant/components/asuswrt/device_tracker.py", line 52, in async_update_info
    self.last_results = await self.connection.async_get_connected_devices()
  File "/usr/local/lib/python3.7/site-packages/aioasuswrt/asuswrt.py", line 168, in async_get_connected_devices
    dev = await self.async_get_arp()
  File "/usr/local/lib/python3.7/site-packages/aioasuswrt/asuswrt.py", line 148, in async_get_arp
    lines = await self.connection.async_run_command(_ARP_CMD)
  File "/usr/local/lib/python3.7/site-packages/aioasuswrt/connection.py", line 37, in async_run_command
    result = await asyncio.wait_for(self._client.run(
AttributeError: 'SshConnection' object has no attribute '_client'

Additional information: