[msan] Fix bad interaction between with-calls mode and chained origin tracking.

Origin history should only be recorded for uninitialized values, because it is
meaningless otherwise. This change moves __msan_chain_origin to the runtime
library side and makes it conditional on the corresponding shadow value.

Previous code was correct, but _very_ inefficient.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211700 91177308-0d34-0410-b5e6-96231b3b80d8