Dmsg delete entry on shutdown

[ersonp]

Did you run make format && make check?

Fixes #

Changes:

• Added dmsgC.Close() in initDmsg in modules
• Removed go dmsgC.Serve(ctx) from NewTransportListener as it was being called twice.

How to test this PR:

1. Checkout dmsg repo on PR #110.
2. In skywire uncomment replace github.com/skycoin/dmsg => ../dmsg in go.mod .
3. Run make dep
4. In skywire-services make log:"debug" in integration/generic/visorA.json
5. Start integration env in skywire-services
6. Run in different terminal

$ redis-cli
> get <PK-OF-VISORA>

7. Wait for 5 mins and check again. It should still be there.
8. Close visor A with Ctrl+C
9. Check for the pk again in redis. The entry should be gone.

This can be tested without integration env on http://dmsg-discovery.myownsky.xyz.

[ersonp]

@jdknives I was looking at the code and it seems like we need a nil check for TransportSetup module since transport_setup_nodes in the config is always null. And if I am not wrong then it only works when transport_setup_nodes has a list of pk's.

[jdknives]

@jdknives I was looking at the code and it seems like we need a nil check for TransportSetup module since transport_setup_nodes in the config is always null. And if I am not wrong then it only works when transport_setup_nodes has a list of pk's.

We need to define a PubKey for that service before we push out the release so it is not null by default. If it is though by user intervention, we should not initialize the module.

[alexadhy]

just proper error checks thing for consistency