Revert "Extract utility function for checking initial value of allocation [NFC]"

This reverts commit 9ce30fe8.  Appears to be causing a problem on a buildbot, revert while investigating.

https://green.lab.llvm.org/green//job/clang-stage1-RA/26818/consoleFull#-1502953973d489585b-5106-414a-ac11-3ff90657619c