Fix testing by using correct env variable names

[matin]

This attempts to resolve the failing tests

@cyberjunky the issue was you and I using different env variable names for the session. As long as you have an active session, the tests will all correctly. I adopted the same naming convention as example.py. Let me know if this works.

[cyberjunky]

I have merged changes manually (could not resolved conflicts via github, due to Resolve conflicts button greyed out (too complex) lol
And did this after login in example.py:

export GARMINTOKENS=~/.garminconnect
make test

But still get errors (different than before) related to unable to decode gzip or something like that

========================================================================== short test summary info ===========================================================================
FAILED tests/test_garmin.py::test_stats - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_user_summary - vcr.errors.CannotOverwriteExistingCassetteException: Can't overwrite existing cassette ('/home/ron/development/python-garminconnect/tests/cassettes/test_user_summary.yam...
FAILED tests/test_garmin.py::test_steps_data - vcr.errors.CannotOverwriteExistingCassetteException: Can't overwrite existing cassette ('/home/ron/development/python-garminconnect/tests/cassettes/test_steps_data.yaml'...
FAILED tests/test_garmin.py::test_floors - vcr.errors.CannotOverwriteExistingCassetteException: Can't overwrite existing cassette ('/home/ron/development/python-garminconnect/tests/cassettes/test_floors.yaml') in...
FAILED tests/test_garmin.py::test_daily_steps - vcr.errors.CannotOverwriteExistingCassetteException: Can't overwrite existing cassette ('/home/ron/development/python-garminconnect/tests/cassettes/test_daily_steps.yaml...
FAILED tests/test_garmin.py::test_heart_rates - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_stats_and_body - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_body_composition - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_body_battery - vcr.errors.CannotOverwriteExistingCassetteException: Can't overwrite existing cassette ('/home/ron/development/python-garminconnect/tests/cassettes/test_body_battery.yam...
FAILED tests/test_garmin.py::test_hydration_data - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_respiration_data - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_spo2_data - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_hrv_data - requests.exceptions.ContentDecodingError: ('Received response with content-encoding: gzip, but failed to decode it.', error('Error -3 while decompressing data: incorrect...
FAILED tests/test_garmin.py::test_download_activity - vcr.errors.CannotOverwriteExistingCassetteException: Can't overwrite existing cassette ('/home/ron/development/python-garminconnect/tests/cassettes/test_download_activit...

[matin]

I'll issue a new PR based on the new changes in master