fix bug in eth_subscribe with 0x prefix and bug in unit test for agen…

[alejoacosta74]

PR description

This PR implement 2 fixes related to bugs when subscribing to events via web3 and the corresponding unit test

1. Fix bug in eth_subscribe with "0x" prefix in contract address

Bug description

A web3 script that subscribes to an ethereum event sends contract address with "0x" prefix, but qtum expects contract address without "0x":

level=debug component=qtum.Client method=waitforlogs
=> qtum RPC request
{
"jsonrpc": "1.0",
"method": "waitforlogs",
"id": "1",
"params": [
null,
null,
{
"addresses": [
"0x086edcf3fc8a042c1b174e941187369d2919e06b"
],
"topics": [
"0d3648bd0f6ba80134a33ba9275ac585d9d315f0ad8355cddefde31afa28d0e9",
null,
null
]
},
0
]
}
<= qtum RPC response
{
"error": {
"code": -32602,
"message": "Invalid hex 160 string"
},
"id": "1",
"result": null
}

Bug fix

In notifier/subscription.go:

	for i, ethAddress := range ethAddresses {
		if strings.HasPrefix(ethAddress.String(), "0x") {
			stringAddresses[i] = strings.TrimPrefix(ethAddress.String(), "0x")
		} else {
			stringAddresses[i] = ethAddress.String()
		}
	}

2. Fix bug in unit tests for websocket subscription

Bug description

After implementing fix described above, unit tests fail for web sockets subscription

Bug fix

The mocked qtum response when testing event subscription should use a contract address without "0x" prefix

internal/tests_common.go

func QtumWaitForLogsEntry(log qtum.Log) qtum.WaitForLogsEntry {
	return qtum.WaitForLogsEntry{
		BlockHash:         GetTransactionByHashBlockHexHash,
		BlockNumber:       GetTransactionByHashBlockNumberInteger,
		TransactionHash:   GetTransactionByHashResponseData.Hash,
		TransactionIndex:  hexutil.MustDecodeUint64(GetTransactionByHashResponseData.TransactionIndex),
		From:              GetTransactionByHashResponseData.From,
		To:                GetTransactionByHashResponseData.To,
		CumulativeGasUsed: hexutil.MustDecodeUint64(GetTransactionByHashResponseData.Gas),
		GasUsed:           hexutil.MustDecodeUint64(GetTransactionByHashResponseData.Gas),
		ContractAddress:   strings.TrimPrefix(GetTransactionByHashResponseData.To, "0x"),
		Topics:            log.Topics,
		Data:              log.Data,
	}
}