Fix: tests: add shellcheck test to distribution

Add the shellcheck test to the distribution, also copy it to the build
dir for oot builds and while where are here, rename it with the 'test_'
prefix to match the rest of the test suite.

Change-Id: Iaeff191022d16ea666c2145aa7e907aeebb6c5ff
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>