Update prune test to account for larger minimum pruning size.
Update prune test to account for larger minimum pruning size.

Create 2MB blocks instead of 1MB blocks.

adpg211/bitcoin-master,deadalnix/bitcoin,bitcoinclassic/bitcoinclassic,deadalnix/bitcoin,deadalnix/bitcoin,deadalnix/bitcoin,zander/bitcoinclassic,adpg211/bitcoin-master,adpg211/bitcoin-master,bitcoinclassic/bitcoinclassic,adpg211/bitcoin-master,bitcoinclassic/bitcoinclassic,bitcoinclassic/bitcoinclassic,zander/bitcoinclassic,zander/bitcoinclassic,zander/bitcoinclassic,zander/bitcoinclassic,deadalnix/bitcoin,deadalnix/bitcoin,bitcoinclassic/bitcoinclassic,zander/bitcoinclassic,adpg211/bitcoin-master,adpg211/bitcoin-master,bitcoinclassic/bitcoinclassic