Fix pe::findContainingProcess for bodies within -1*epsilon of a block edge

Assume a block size B, domain size L and a body on the second block that is at B-std::numeric_limits<real_T>::epsilon*L. Then block.getAABB().contains() is false because the second block does not contain the body, but in the attempt to find the responsible neighbor block, findContainingProcess uses mapToPeriodicDomain, which calculates something like (B-std::numeric_limits<real_T>::epsilon*L + L) % L. Due to finite precision this is equal to B and inside the second block.

Previously, this meant that the body became owner-less and was deleted. Of course, that's wrong.