Fix two test-only leaks found by LSan.

The result of getBufferForFile() must be freed.
(Should we change functions that expect the caller to assume ownership so
that they return unique_ptrs instead? Then the type system makes sure we get
this right.)


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207074 91177308-0d34-0410-b5e6-96231b3b80d8