nwo.GetConfigBlock retry until success
nwo.GetConfigBlock retry until success

This function is flakey when there isn't a current Raft
leader and can return SERVICE_UNAVAILABLE when that is the
case. Instead, retry the fetch until it succeeds.

FAB-18287 #done

Signed-off-by: Will Lahti <f19a2779710675aad3df5c81e4ecfde11707e3aa@us.ibm.com>

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