Enable support for installcheck.

Enable support for installcheck.

Enable execution of tests via `make installcheck`, i.e. against a fully
installed
LTTng.

The patch simply adds the same rule to the installcheck target that is
used for check.  Testing with an OpenEmbedded build shows the unit_tests
suite to work fine, while the fast_regression suite contains many
failures not present when run as `make check`.

Stefan Seefeld (1):
  Enable support for installcheck.

Signed-off-by: Stefan Seefeld <stefan_seefeld@mentor.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>