Closure adjustments for segmentation faults

Replaced a number of user_call_func() calls for closures and replaced them with {ClosureName}(). This resolved a number of unit-tests that were giving segmentation faults.

See #2914.

Not all of the tests work now, the MicroMvcTest::testMicroNotFound_T169 still seg faults on the NotFoundHandler closure, no matter what I do with it. The only way to have the test pass is to replace the closure with a boolean and not have it execute the closure.