[#190] common: Check `NeoFS` role for the next block

Current height makes it impossible to change
role and make some operations in one block.
Also, it may lead to accepting some operations
that are approved by already not valid alphabet.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

common/ir.go

@@ -32,7 +32,7 @@ func InnerRingInvoker(ir []IRNode) interop.PublicKey {
 // in side chain.
 func InnerRingNodes() []IRNode {
 	blockHeight := ledger.CurrentIndex()
-	list := roles.GetDesignatedByRole(roles.NeoFSAlphabet, uint32(blockHeight))
+	list := roles.GetDesignatedByRole(roles.NeoFSAlphabet, uint32(blockHeight+1))
 	return keysToNodes(list)
 }