logaggregator: Fix race in CloseNotify usage
logaggregator: Fix race in CloseNotify usage

Get the channel in the main channel so we don’t race with the request
finishing.

Signed-off-by: Jonathan Rudenberg <3692bfa45759a67d83aedf0045f6cb635a966abf@titanous.com>
benbjohnson/flynn,flynn/flynn,lmars/flynn,benbjohnson/flynn,philiplb/flynn,lmars/flynn,flynn/flynn,benbjohnson/flynn,flynn/flynn,philiplb/flynn,philiplb/flynn,benbjohnson/flynn,philiplb/flynn,philiplb/flynn,flynn/flynn,lmars/flynn,flynn/flynn,benbjohnson/flynn,lmars/flynn,benbjohnson/flynn,lmars/flynn