Approving a pending device created a Node with check_method=NULL, so
the status scheduler silently skipped it (scheduler.py:64 filters
falsy check_method) and the bubble stayed grey forever.
Default to 'ping' when the device has an IP, in both single and bulk
approve paths. Also persist caller-supplied check_method/check_target
in the single-approve path.
Add regression tests asserting default check_method='ping' after
approval for both endpoints.
Pouzor
ebdf6cb55b