torture: Print informative message for test without recheck file

torture: Print informative message for test without recheck file

If a type of torture test lacks a recheck file, a bash diagnostic is
printed, which looks like a torture-test bug.  This commit gets rid of
this false positive by explicitly checking for the file, invoking it if
it exists, otherwise printing an informative non-diagnostic message.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>