There is no longer any reason for these to be intertwined.
This deliberately avoids touching some files as much as possible because
they are super tangled and due to be replaced. Those files are:
* fdroidserver/build.py
* fdroidserver/update.py
# Conflicts:
# tests/testcommon.py
# Conflicts:
# fdroidserver/btlog.py
# fdroidserver/import_subcommand.py
The start up sequence of processes that are based on the .fdroid.* metadata
is a bit different, so this ensures that the environment variables get
properly initialized in all cases.
This also creates a single function where the environment is set. Before
it was being set in multiple places across multiple files.
