Simplify boolean expressions

Simplify boolean expressions

* Drop explicit “? true : false” (or the reverse).
* Simplify “if (...) return true; else return false;”.
* Simplify tail “if (...) return false; return true;”.
* Simplify explicit comparisons with true or false.

This was mostly done automatically by IntelliJ.

Change-Id: Ib252f58f2feb2fe6e05e89ad90ab11f85b5e3289
Signed-off-by: Stephen Kitt <skitt@redhat.com>