Fix #1320: Allow multiple message sends in TestAdapter

This commit eliminates confirmation messages from the JS slave to the
JVM orchestrator on client messages (the "msg:" message). The slave
may still send a fail message but does not confirm reception of the
message anymore. This avoids having nested reception loops that expose
races.
Actually set local runner to null after use
Fix #1325: Repeatedly decode incoming Node.js Com messages
Get rid of ugly isAlive hack
Fix #1328: Handle socket errors in Node.js com