[Orc] Make OrcMCJITReplacement::addObject calls transfer buffer ownership to the

ObjectLinkingLayer.

There are a two of overloads for addObject, one of which transfers ownership of
the underlying buffer to OrcMCJITReplacement. This commit makes the ownership
transfering version pass ownership down to the ObjectLinkingLayer in order to
prevent the issue described in r227778.

I think this commit will fix the sanitizer bot failures that necessitated the
removal of the load-object-a.ll regression test in r227785, so I'm reinstating
that test.

llvm-svn: 227845