torture: Suppress "find" diagnostics from torture.sh --do-none run

torture: Suppress "find" diagnostics from torture.sh --do-none run

When torture.sh is told to do nothing, it produces a couple of distracting
diagnostics from the "find" command:

	find: ‘’: No such file or directory
	find: ‘’: No such file or directory

This is pointless chatter and could cause confusion.  This commit therefore
suppresses these diagnostics when there is nothing to find.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>