Revert a C API difference that I incorrectly introduced.

LLVMGetBitcodeModuleInContext should not take ownership on error. I will
try to localize this odd api requirement, but this should get the bots green.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211213 91177308-0d34-0410-b5e6-96231b3b80d8