sci-misc/vitables: use pytest-xdist to run tests in subprocesses

There is a random segfault in the testsuite. If I run

```
while FEATURES=test emerge -1 vitables; do :; done
```

after a few successful runs, it fails with

```
tests/test_vtgui.py::TestVTGui::test_dockWidget Fatal Python error: Segmentation fault
```

This does NOT fix the tests. It does, however, allow pytest to process
the entire test session and summarize as e.g.

> worker 'gw6' crashed while running 'tests/test_logger.py::TestLogger::test_write'

Bug: https://bugs.gentoo.org/892886
Signed-off-by: Eli Schwartz <eschwartz@gentoo.org>

0 files changed, 0 insertions, 0 deletions