Fix: don't enable a channel if a session was already started

This removes also the check done to start the session if it was started
before.

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: possible infinite loop in disable ust event

Fixes #575

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: if relayd is unreachable, disable consumer for the session

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: build path for unit test to build out of tree

Signed-off-by: David Goulet <dgoulet@efficios.com>
Update version to v2.2.0

Signed-off-by: David Goulet <dgoulet@efficios.com>