Fix SpentCoinState.Clone

[shargon]

Close #1368

[shargon]

@superboyiii could you test this?

[cloud8little]

@superboyiii could you test this?

@shargon is there any user scenario for this?

[shargon]

The UT ensure that both object can be changed without change the content of the other, I think that we need a backward compatibility test.

[superboyiii]

@shargon @nicolegys is focusing on test of this PR, something still needs deep investigation. She will give you final result as soon as possible.

[nicolegys]

TestResults:
Mainnet: compatible with 2.10.3
Testnet: 7 files different with 2.10.3/master2.x

Differences_pr1369.zip

It is strange that this pr is compatible with pr 1376 both on mainnet and testnet.

[nicolegys]

I found out what the problem was.
My 2.10.3 testnet node didn't install RpcNep5Tracker plugin, but pr1369/pr1376 testnet node installed RpcNep5Tracker.
I have tried several times, found out that the storage files of testnet were different when with and without RpcNep5Tracker. It's the issue of RpcNep5Tracker.
I'll sync two mainnet nodes to make sure whether the same problem exists.

[shargon]

Thanks @nicolegys we can wait, no problem :)

[nicolegys]

@shargon Thank you for your patience in waiting for the result.
The phenomenon didn't appear on mainnet.
Anyway, this is another issue. For me, the Compatibility test of pr1369/pr1376 have passed.

[superboyiii]

@shargon This PR is able to merge, but seems gitcheck is bogging down.

[shargon]

I think that neo2 is with travis and was down, @erikzhang could you help us for merge this?