Tests: Fix nprocesses applications shutdown

The nprocesses test is using the SIGPIPE signal to shutdown the
spawned child applications. This is done in order to silence
the shell message such as this one:

"nprocesses/test_nprocesses: line 79: 26458 Terminated"

This mechanism is broken on systems where the SIGPIPE default handler
is overriden (thus no application shutdown occurs) in the executing
environment. This could lead to stale applications polluting the system
and causing heratic behavior in subsequent tests.

This commit add a loop and check that all the spawned applications have
been successfully killed.

Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Tests: Add Python test_utils module

Basic Python test framework based on the lttng-tools Python bindings
that facilitates the creation of a tracing session saving its trace in
a temporary location, the activation of events in the UST domain and
clean teardown of the test session.

Also provides basic TAP output facilities.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add "linking" ust regression test

Based on the "demo" test formerly part of lttng-ust.
Tests userspace tracing with directly, statically and dynamically linked
providers. Also meant as an exemple of building and tracing an application
with all types of provider linking.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add "daemon" ust regression test

Based on the "daemon" test formerly part of lttng-ust.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add "exit-fast" ust regression test

Based on the "exit-fast" test formerly part of lttng-ust.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add "fork" ust regression test

Based on the "fork" test formerly part of lttng-ust.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add "libc-wrapper" ust regression test

Based on the "test-libustinstr-malloc" test formerly part of lttng-ust.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>