Revert "Fix an issue where LLDB would run out of stack space ..."

This commit introduced an infinite recursion in
ValueObjectChild::CanUpdateWithInvalidExecutionContext (because FollowParentChain also considers
the current object), which broke nearly all the tests. Ignoring the current object removes the
recursion, but two tests still time out (TestDataFormatterLibcxxList.py and
TestValueObjectRecursion.py) for some reason. Reverting for now.

llvm-svn: 243102