When running on multiple CPUs, some asserts fail - issue with received_wei

[loredanacirstea]

(most probably a tests issue after changing how we end the auction)

Following asserts fail only when running tests with https://pypi.python.org/pypi/pytest-xdist -n 4

raiden-token/tests/test_auction.py

Line 685 in 6fbd9eb

assert received_wei == funds_at_price

assert 5000000002 == 5000000000

raiden-token/tests/test_auction.py

Line 691 in 6fbd9eb

assert int(total_tokens_claimable) == auction.call().num_tokens_auctioned()

assert 5000000002000000000000000 == 5000000000000000000000000

raiden-token/tests/test_auction.py

Line 729 in 6fbd9eb

assert unclaimed_token_supply == unclaimed_tokens

assert 4999999999000000000000000 == 5000000001000000000000001