Add LINSTOR controller and satellite helpers - #22

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Before this fix, this test was unstable and could fail.
It's wiser to wait for the server to close instead of spamming calls.

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

The goal of this change is to continue retrying calls in the event
of network loss, while also allowing this feature to be disabled
for calls that are not idempotent and require more intelligence
on the caller side.

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Without that we can trigger this error:
```
> mypy
tests/rpc/conftest.py: error: Duplicate module named "conftest" (also at "tests/backends/conftest.py")
tests/rpc/conftest.py: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#mapping-file-paths-to-modules for more info
tests/rpc/conftest.py: note: Common resolutions include: a) using `--exclude` to avoid checking one of them, b) adding `__init__.py` somewhere, c) using `--explicit-package-bases` or adjusting MYPYPATH
Found 1 error in 1 file (errors prevented further checking)
```

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Executables were run through hardcoded absolute paths, it only works on some distributions.
`ss` is in `/usr/bin` on the GitHub Ubuntu runners, instead of in `/usr/sbin`
on XCP-ng so the LINSTOR controller tests are marked as failed.

Now "/etc/os-release" is used to find alternate OS specific paths instead.

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>