Command `sky status` confusion with local clusters

[michaelzhiluo]

When using only Sky onprem for the first time, sky status shows:

No existing clusters.

Local clusters:
NAME                USER  HEAD_IP         RESOURCES                 COMMAND                         
hello               test  54.167.205.58   [(no GPUs)]               sky launch -c hello -- echo...

This is confusing for initial users since no existing clusters conflicts with local clusters.