Fix: memleaks in channel/event notify

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: add missing free causing a memleak

Also remove a unused variable in the ust registry event structure.

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: memleak in the UST registry

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: memleak in liblttng-ctl visit_node_load()

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>