Timezone environment variable not being honored

[dougbtv]

@arainero reported that the Timezone environment variable, as found @ https://github.com/sipcapture/homer-docker/blob/master/homer.env#L2 is apparently not being honored.

1. Need to reproduce and fix
2. Need to add tests to verify it works

Issue broken out from report in #54

[pdf]

Suspect this is due to HOMER_TIMEZONE being statically defined in preferences.php everywhere, rather than populated from env in configuration.php.