torture: Fix incorrectly redirected "exit" in kvm-remote.sh

The "exit 4" in kvm-remote.sh is pointlessly redirected, so this commit
removes the redirection.

Fixes: 0092eae4 ("torture: Add kvm-remote.sh script for distributed rcutorture test runs")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>