Fix standard (no remote barrier) parity flip bug

A bug was introduced when moving from statically assigning the parity to wait
for on the update side (first even, then odd) to a model trying to deal the
single flip test case. It occurs that when busy-looping, the parity flip
occurred when it should not.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>