[MERGE] lttng snapshot command fails if session is not in no output mode

Signed-off-by: David Goulet <dgoulet@efficios.com>
[HEAD MERGE] Flight recorder feature

Signed-off-by: David Goulet <dgoulet@efficios.com>
[HEAD MERGE] Kernel snapshot support

**ADD CHANGELOG**

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>
[MERGE] add kernel consumer destroy channel. NOT COMPLETED

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