Merge branch 'master' into t

* master:
  tests: Don't try to access db.storage when automatically closing connections
  bigfile/py: Garbage-collect BigFile <=> BigFileH cycles
  bigfile/py: Move PyVMA's support for cyclic GC close to pyvma_dealloc
  t/tfault-run: Require bash
  t/tfault-run: Clear state from previous run before starting
  Add way to run tests via nxdtest