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

[spoonincode]

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 #553, in extreme cases it could remove a user's wallet (what I'm worried #704 might have done).

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.

[spoonincode]

Transferred to Leap repo