Fix network order with Active status

[jeremyletang]

We had an issue where network order where not fully matched (matched up to the average price)
We now make the NETWORK order behave as a MARKET order, and set the average price at the end of uncrossing.

closes #2060

[vega-ci-bot]

system-tests failed.

=== Test summary ===
../../grpcTesting/governance/newAssetTests.py .                          [100%]
../../grpcTesting/governance/newMarketGovTests.py .....................x [ 47%]
........................                                                 [100%]
../../grpcTesting/governance/newMarketTradesTests.py ............        [100%]
../../grpcTesting/margins/marginsTests.py F.                             [100%]
 testMarginLevelStoppedFOK 
../../grpcTesting/markets/marketsTests.py ..............                 [100%]
../../grpcTesting/orders/amendOrdersTests.py ........................... [ 87%]
....                                                                     [100%]
../../grpcTesting/orders/cancelOrdersTests.py .......................    [100%]
../../grpcTesting/orders/generalOrdersTests.py .............             [100%]
../../grpcTesting/orders/limitOrdersTests.py ...........                 [100%]
../../grpcTesting/orders/marketOrdersTests.py ........                   [100%]
../../grpcTesting/orders/mixedOrdersTests.py .....................       [100%]
../../grpcTesting/orders/negativeOrdersTests.py ........................ [ 57%]
....x.........s...                                                       [100%]
../../grpcTesting/parallel/submitParallelOrdersTests.py ........         [100%]
../../grpcTesting/parties/partiesTests.py ..                             [100%]
../../grpcTesting/trading/positionsTests.py ..                           [100%]
../../grpcTesting/trading/tradesTests.py ............                    [100%]
../../grpcTesting/wallet/walletTests.py ................................ [ 91%]
...                                                                      [100%]
../../rest/orders/negativeOrdersTests.py .                               [100%]