Document pitfalls for private changes and discourage using them for security fixes
Document pitfalls for private changes and discourage using them for security fixes

Reason for cherry-pick: the behavioral change affected 3.0 already; see
also change I4f9ec7890c152ac9d.

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Change-Id: I2a71b66a3f4b50aaa73b415f46de4f4296d4389b
(cherry picked from commit 8bb24fe371a783d61976a09fbc12a0ee28ee01db)

qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit