Using bool variable with queryAdd for elements appearing more than once can yield false -> true

[cemitch99]

For a lattice with an element (named, eg, "ap1") that appears more than once in the lattice, the use of lines such as:

bool has_old_xmax = pp_element.queryAdd("xmax", aperture_x);
amrex::Print() << "has_old_xmax" << " " << has_old_xmax << std::endl;

in InitElement.cpp shows that the value of has_old_xmax can change from false to true, even if "xmax" does not appear anywhere.

This appears in the context of PR #802. It has no affect on Python-based input.