[FAB-15626] avoid use of testing.T in async logs
[FAB-15626] avoid use of testing.T in async logs

- Replace use of NewTestLogger with a fabric logger that writes to a
  gbytes.Buffer.
- Reset production logger at end of test

Signed-off-by: Matthew Sykes <fb2dd171fe47bac8d5b55d1d785c243b0892e206@gmail.com>
Change-Id: I4255a6318a529587b5d4fd3a6a34964a1868c27c

stemlending/fabric,muralisrini/fabric,stemlending/fabric,manish-sethi/fabric-sidedb,stemlending/fabric,jimthematrix/fabric,jimthematrix/fabric,muralisrini/fabric,binhn/fabric,stemlending/fabric,manish-sethi/fabric,manish-sethi/fabric-sidedb,muralisrini/fabric,hyperledger/fabric,manish-sethi/fabric-sidedb,binhn/fabric,manish-sethi/fabric-sidedb,binhn/fabric,manish-sethi/fabric-sidedb,hyperledger/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,manish-sethi/fabric