a bug in the method ChassisExist

[DWC666]

Expected Behavior

when the chassis not exist, the method ChassisExist return false

Actual Behavior

the method ChassisExist return true

Steps to Reproduce the Problem

if the output is a empty str, the method will return true, because len(strings.Split(output, "\n")) is 1, not 0.

Additional Info

• Kubernetes version:

  Output of kubectl version:

  (paste your output here)
  

• kube-ovn version:

v1.11.3

- operation-system/kernel version:

**Output of `awk -F '=' '/PRETTY_NAME/ { print $2 }' /etc/os-release`:**
**Output of `uname -r`:**

(paste your output here)

<!-- Any other additional information -->

[zhangzujian]

Could you please commit a PR to fix it?

[DWC666]

@zhangzujian
okay