go test: fails randomly in channeler_test.go with Errorf: timeout

[cyrilleverrier]

Steps to reproduce:
make test / go test -v / go test -v -race

Some of the tests fail randomly with t.Errorf("timeout") when trying to receive a new message from the subscriber channel.

Explanation:
A message is sent to the SendChan just after the subscriber with a RecvChan has been created.
I guess that the subscriber doesn't have enough time to run its internal go-routine and the message sent in the unit test is lost.

New functions like NewSubChanneler should exit only after the go-routine in the subscriber is polling new messages from the zeromq sock.