clang-refactor-test: dispose of the TU
clang-refactor-test: dispose of the TU

rdar://35618000
(cherry picked from commit 65703087ccfeef001abc80fbff775f338a18c7e3)

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang