Revert "Fix that the ini writer produces invalid configuration files"

This reverts commit 9bec8e3c27702914f964a6be607ee12cb379d1bb.
Ensure that the ini writer deletes properties properly

The fix for #5958 introduced with commit 6aaff6b3 caused the property
deletion of the PreservingIniWriter be even more faulty than before. The
actual fix for this issue is an improved procedure for how properties are
deleted as the initial implementation suffered from a few
misunderstandings in how properties in Zend_Ini files need to be handled.

fixes #6599
fixes #6601
fixes #6600
fixes #6598
fixes #6614