Make image downlink not fault hercules idle thread if wifi is lost during downlink

[zCoCo]

Currently a hack is used to halt the idle thread from returning to the camera until NM queue drains (to prevent overfilling and dropped lines). But, the queue won't drain if network is lost.

Since RC9 (which may be the final upload) is imminent, a cheap solution is to just drop lines if we're not connected.