[LLDB] Attempt to fix DumpDataExtractorTest

This test was broken by 710276a2 because
DumpDataExtractor now accesses the Target properties, which someone ends
up relying on the file system.

This is an instance of this error https://lab.llvm.org/buildbot/#/builders/96/builds/45607/steps/6/logs/stdio

I cannot reproduce this locally, but it seems that the error happens
because we are not initializing the FileSystem and the Host as part of
the test setup.