boot_node:monitor_parent shells to nonexistant kill cmd

See https://github.com/apache/couchdb/blob/master/dev/boot_node.erl#L30-L38 for the ugly.

There is no direct kill -0 equivalent on Windows. Instead we get something like tasklist /fi "PID eq 1234" which doesn't return an error code != 0 if a match is not found, we actually have to parse the output returned. Bleah.