If running `up` in foreground mode (i.e. not `-d`),
when exiting via `Ctrl-C`, Compose stops all the
services it launched directly as part of that `up`
command.
In one of the E2E tests (`TestUpDependenciesNotStopped`),
this was occasionally flaking because the stop
behavior was racy: the return might not block on
the stop operation because it gets added to the
error group in a goroutine. As a result, it was
possible for no services to get terminated on exit.
There were a few other related pieces here that
I uncovered and tried to fix while stressing this.
For example, the printer could cause a deadlock if
an event was sent to it after it stopped.
Also, an error group wasn't really appropriate here;
each goroutine is a different operation for printing,
signal-handling, etc. If one part fails, we don't
actually want printing to stop, for example. This has
been switched to a `multierror.Group`, which has the
same API but coalesces errors instead of canceling a
context the moment the first one fails and returning
that single error.
Signed-off-by: Milas Bowman <milas.bowman@docker.com>
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