[CBR-475] Fix tests for synchronization
[CBR-475] Fix tests for synchronization

The `waitAny` function calls were killing threads, causing some work to
not be completed.

input-output-hk/pos-haskell-prototype,input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/cardano-sl,input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl