Attributes: Avoid infinite recursion on non-lowercase attribute getters

Attributes: Avoid infinite recursion on non-lowercase attribute getters

Attribute hooks are determined for the lowercase versions of attribute names
but this has not been reflected in the bool attribute hooks. The code that
temporarily removed a handler to avoid an infinite loop was removing an
incorrect handler causing stack overflow.

Fixes gh-3133
Refs gh-2914
Refs gh-2916
Closes gh-3134