Revert "fix(ngOptions): skip comments when looking for option elements"

This reverts commit 7f3f3dd3ebcc44711600ac292af54c411c3c705f.
The fix only fixed a specific case and exhibited a flawed logic
(namely skipping every option if the emptyOption is a comment).
See https://github.com/angular/angular.js/issues/12190#issuecomment-145877914

Conflicts:
	test/ng/directive/ngOptionsSpec.js