Add grain to list LVM volumes implement issue 57629

[piterpunk]

What does this PR do?

This initial support implements a grain called "lvm" which returns a dictionary with the volume groups, each one with a list of their logical volumes inside.

LVM is an important information about a Linux machine. Usually Linux servers have most or all their disk filesystems using a logical volume as mountpoint.

What issues does this PR fix or reference?

Implements and resolves #57629

New Behavior

To have a grain with the list of LVM volumes:

root@marvin:~# salt-call grains.get lvm
local:
    ----------
    marvinvg00:
        - opt
        - root
        - swap
        - tmp
        - usr
        - var
    marvinvg01:
        - home
        - srv
        - usrlocal

Merge requirements satisfied?

salt-runtests-20200610192428.log

Commits signed with GPG?

No

[DmitryKuzmenko]

@piterpunk thank you for contribution! Could you please cover your changes with tests?

[piterpunk]

@piterpunk thank you for contribution! Could you please cover your changes with tests?

Hi Dmitry, tests added. I hope they are Ok.

The tests for Linux and AIX are not the same because in AIX the LVM is part of base system, so it's always installed and with at least one volume group created.

[DmitryKuzmenko]

@piterpunk thank you! I've restarted macos x mojave tests the failure looked not related to your changes.

[piterpunk]

@DmitryKuzmenko , seeing the console logs, the failure at MacOSX seems to be while setting up the environment, it didn't even began to run the tests.

[DmitryKuzmenko]

@piterpunk Everything passed. Thank you for your work!

[piterpunk]

@DmitryKuzmenko , I did some changes to pass the new pre-commit tests, removing the usage of six and Py2 support.

[DmitryKuzmenko]

@piterpunk thank you!

[DmitryKuzmenko]

Tests are passing now (again).

[piterpunk]

Tests are passing now (again).

@DmitryKuzmenko , it's a lottery. Most tests fails by timeout, no available space, or error cloning the repository. I don't know if and how I can re-run only the failed tests, so my alternative is to merge from master until all tests passed.