1. Using MNT_FORCE flag does not make sense for nsfs. Using MNT_DETACH
though might help.

2. When -check.vv is added to TESTFLAGS, there are a lot of messages
like this one:

> unmount of /tmp/dxr/d847fd103a4ba/netns failed: invalid argument

and some like

> unmount of /tmp/dxr/dd245af642d94/netns failed: no such file or directory

The first one means directory is not a mount point, the second one
means it's gone. Do ignore both of these.

Signed-off-by: Kir Kolyshkin <[email protected]>

A timer is leaking on every daemon start and stop.
Probably nothing major, but given the amount of
daemon starts/stops during tests, it's better to
be accurate about it.

Signed-off-by: Kir Kolyshkin <[email protected]>

This is repeated 6 times in different tests, with slight
minor variations. Let's factor it out, for clarity.

While at it, simplify the code: instead of more complex
parsing of "docker swarm init|update --autolock" output (1)
and checking if the key is also present in
"docker swarm unlock-key" output (2), get the key
from (2) and check it is present in (1).

Signed-off-by: Kir Kolyshkin <[email protected]>

......

Signed-off-by: Kir Kolyshkin <[email protected]>

When starting docker daemons for swarm testing, we disable iptables
and use lo for communication (in order to avoid network conflicts).

The problem is, these options are lost on restart, that can lead
to any sorts of network conflicts and thus connectivity issues
between swarm nodes.

Fix this. This does not fix issues with swarm test failures, but
it seems they appear are less often after this one.

Signed-off-by: Kir Kolyshkin <[email protected]>