torture: Extract kvm-test-1-run-qemu.sh from kvm-test-1-run.sh

Currently, kvm-test-1-run.sh both builds and runs an rcutorture kernel,
which is inconvenient when it is necessary to re-run an old run or to
carry out a run on a remote system.  This commit therefore extracts the
portion of kvm-test-1-run.sh that invoke qemu to actually run rcutorture
and places it in kvm-test-1-run-qemu.sh.

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