supply blocking mode from argument

[todo]

fabric-peer-ext/mod/peer/gossip/state/state.go

Lines 86 to 91 in 1a12f67

	//TODO supply blocking mode from argument
	return &gossipStateProviderExtension{chainID, mediator, support, true}
	}
	type gossipStateProviderExtension struct {
	chainID string

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This issue was generated by todo based on a TODO comment in 1a12f67 when #182 was merged. cc @sudeshrshetty.