[msan] Fix truncated stack trace in chained origin reports.

This is a leftover from the times when the next (chained) origin id
was stored as the last frame of a stack trace.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@211878 91177308-0d34-0410-b5e6-96231b3b80d8