Consolidate CreateTempName_Impl and lcl_createName more faithfully

This is a follow-up to fcf455d4efde077bb2b092b607de12ebfc350275 "Consolidate
CreateTempName_Impl and lcl_createName," which apparently lead to hard-to-
diagnose sporadic "make check" failures on some machines.  Hope is that bLock
now more carefully tracking the behavior of the original two functions fixes
that.

Change-Id: I37ba00545f5921fd603ff9f1ea46927c42e88899