Fix: Resource leak in ust registry

Fix coverity issue 1019918.

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: dereference after null check in UST registry

Fix coverity issue 1132896.

Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: unchecked return value in ust app delete

Fix coverity issue 1132897.

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