Addition of ability to run Lithops on shared multi-user machines.

[spiogit]

The current behaviour of Lithops is to create an unqualified subdirectory in /tmp for tracking various bits of information. When more than one user one a machine run a globally installed framework, this causes permission issues:

$ lithops test ... [INFO] config.py:131 -- Lithops v2.7.2.dev0 ... Traceback (most recent call last): ... PermissionError: [Errno 13] Permission denied: '/tmp/lithops/storage/lithops.jobs' ... Traceback (most recent call last): ... PermissionError: [Errno 13] Permission denied: '/tmp/lithops/cleaner/tmpkjj_17vq'

The patch fixes that by qualifying the directory with a username component. (Security versus comfort trade-off: Using the UID may be safer but is less readable than the $USER value.) Related to that, the patch also makes it possible to configure Lithops for all users without having to set LITHOPS_CONFIG_FILE, while still permitting them to override with their own configurations. The use of a default file in /etc follows conventions.

With this patch, Lithops becomes usable e.g. in classroom settings.

All but one unit tests pass. The one that bails out might be unrelated to the patch.

====================================================================== FAIL: test_storage_list_objects (lithops.tests.test_storage.TestStorage)

Traceback (most recent call last): File "/usr/local/lib/python3.10/dist-packages/lithops-2.7.2.dev0-py3.10.egg/lithops/tests/test_storage.py", line 177, in test_storage_list_objects self.assertEqual(extract_keys(foo_objects), sorted([ AssertionError: Lists differ: ['__lithops.test/foo_baz', 'lithops.test/foo/baz', 'litho[46 chars]baz'] != ['lithops.test/foo/bar/baz', 'lithops.test/foo/baz', '__l[46 chars]baz']

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[JosepSampe]

Thanks @spiogit

[JosepSampe]

Storage test fixed in #1016