torture: Don't cap remote runs by build-system number of CPUs

Currently, if a torture scenario requires more CPUs than are present
on the build system, kvm.sh and friends limit the CPUs available to
that scenario.  This makes total sense when the build system and the
system running the scenarios are one and the same, but not so much when
remote systems might well have more CPUs.

This commit therefore introduces a --remote flag to kvm.sh that suppresses
this CPU-limiting behavior, and causes kvm-remote.sh to use this flag.

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