Fix: test: base-path tests are not run

Fix: test: base-path tests are not run

Observed issue
==============

The base-path tests are never run during `make check`.

Cause
=====

Albeit 2a1668643ca94195d5c3889d0337e19165805a42 [1] introduces the tests,
the test file is not added to the test list.

Solution
========

Add the test file to the test list.

One of the substest is failing.

  not ok 20 - Snapshot recorded
  #   Failed test 'Snapshot recorded'
  #   in .//../../../utils/utils.sh:lttng_snapshot_record() at line 1468.
  ok 21 - Destroy session ust_app_snapshot_base_path
  not ok 22 - Validate trace for event tp:tptest

This is caused by the removal of `trace_path=$2` in
c28fcefd993b7539716bb5cd9557a08a217ec463 [2]. The removal is most
probably a merge error or simply a mistake on my end. This commit revert
that change.

Also add load-stream-extra-path.lttng in EXTRA_DIST.

Known drawbacks
=========

None

References
==========
[1] https://github.com/lttng/lttng-tools/commit/2a1668643ca94195d5c3889d0337e19165805a42
[2] https://github.com/lttng/lttng-tools/commit/2a1668643ca94195d5c3889d0337e19165805a42

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I255908165d59e02e0e11b123d3538a74f53fb584