torture: De-capitalize TORTURE_SUITE

Although it might be unlikely that someone would name a scenario
"TORTURE_SUITE", they are within their rights to do so.  This script
therefore renames the "TORTURE_SUITE" file in the top-level date-stamped
directory within "res" to "torture_suite" to avoid this name collision.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>