prevent access to ~/eosio-wallet/ & ~/.local/share/eosio during CI test runs

[spoonincode]

This is a transfer of eosnetworkfoundation/mandel#770

Tests should never access nodeos' and keosd's default config & data directories (~/.local/share/eosio & ~/eosio-wallet respectively) . At best it can create spooky problems such as eosnetworkfoundation/mandel#553, in extreme cases it could remove a user's wallet (what I'm worried eosnetworkfoundation/mandel#704 might have done in very specific conditions).

CI must prevent access to these directories so that tests violating this rule fail as an indicator to us that the test needs fixing.

Bonus points for using something like FUSE to make sure an application even so much as taking a sniff 👃 with opendir() will cause some sort of catastrophic test failure.