Some truffle tests pass on ganache, but fail on etheno

[ggrieco-tob]

In some cases, truffle tests fail in etheno, but work in ganache. To reproduce:

1. Get the latest balancer-core revision and install all the dependencies (yarn)
2. Install ganache and ganache-cli
3. Start ganache in another terminal: ganache --deterministic --gasLimit 10000000
4. Run yarn test. All the tests will pass. for instance:

   Contract: BFactory
   Factory
   ✓ BFactory is bronze release
   ✓ isBPool on non pool returns false
   ✓ isBPool on pool returns true
   ✓ fails nonAdmin calls collect (42ms)
   ✓ admin collects fees (477ms)
   ✓ nonadmin cant set blabs address
   ✓ admin changes blabs address (51ms)
   

5. Kill ganache and start etheno in another console: etheno --ganache --ganache-args "--deterministic --gasLimit 10000000" -x out.json
6. Run yarn test. Some of the tests will fail:

  Contract: BFactory
    Factory
      ✓ BFactory is bronze release
      ✓ isBPool on non pool returns false
      ✓ isBPool on pool returns true
      1) fails nonAdmin calls collect
    > No events were emitted
      ✓ admin collects fees (339ms)
      2) nonadmin cant set blabs address
    > No events were emitted
      ✓ admin changes blabs address (56ms)