Detect incorrect cycle counting

Detect incorrect cycle counting

When threads are not pinned to cores, the wallcycle counting can get
messed up on machines where the cycle counters are not synchronized
between the cores. Since it's difficult to detect thread pinning on
all architectures and without pinning the counting can be correct on
synchronized machines, we try to detect incorrect counters. We only
detect negative cycle counts, but that should catch nearly all cases.
When we deteced an invalid count, we ignore the cycles counted and do
not print the cycle accounting table. Dynamic load balancing is never
disabled, because a few incorrect load measurements do not cause
problems here.

Fixes #1821

Change-Id: I076ad685a043f1f0b913a9b089ebea43a62534f5