Cristian Adam authored Jul 16, 2019 and Brad King committed Jul 16, 2019

The module mode fallback added by commit 22e65d10 (find_package: Fixed
CMAKE_FIND_PACKAGE_PREFER_CONFIG Module fallback, 2019-06-13,
v3.15.0-rc2~6^2) should not be used unless the `find_package` call
allows module mode.  Doing so can lead to infinite recursion if a find
module tries to call config mode with `find_package(...  NO_MODULE)`.
Fix the logic and add a test case.

Fixes: #19478