Container console exec custom command say "no such exec" if process finish too quickly

[linquize]

Bug description

Container console exec a custom command
If process finishes within 1 second,
Red error "no such exec" will show and go back to Disconnected state.
However, if process finishes more than 1 second,
No error but not go back to Disconnected state.

Expected behavior
No Red error, and back to Disconnected state automatically

Steps to reproduce the issue:

Steps to reproduce the behavior:

1. Go to Container Console
2. Tick Custom Command
3. Enter custom command ps (should finish immediately)
4. The command is executed successfully
5. See red error "no such exec"
6. Also try custom command sleep 1 (should finish in 1 second), same error will occur
7. But if try custom command sleep 2 (should finish in 2 seconds), no error but cannot go back to Disconnected state automatically.

Technical details:

• Portainer version: 1.19.2
• Docker version (managed by Portainer): 18.06
• Platform (windows/linux): Ubuntu 16.04
• Command used to start Portainer (docker run -p 9000:9000 portainer/portainer):
• Browser: Firefox 63