HHH-8364 exclude-unlisted-classes parsing handles content incorrectly

Parsing for `exclude-unlisted-classes` handles content within the element incorrectly. The value correctly defaults to `false`. `<exclude-unlisted-classes />` and `<exclude-unlisted-classes>true</exclude-unlisted-classes>` are correctly parsed as `true`. However, `<exclude-unlisted-classes>false</exclude-unlisted-classes>` is incorrectly also parsed as `true`. This commit fixes that.