Wallet Replicatation from server 1 to server moving wallet.dat

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### Describe the issue
I'd like move my bitcoin cash wallet from one server to the other using the cli.

Server 1: bitcoin abc: 0.17.2. Server 2: bitcoin abc: 0.18.0

I have done the following: 1. ran the command: backupwwallet "myfile.dat" on server 1 successfully. 2. copy the "myfile.dat" to server 2. 3. rand the command: importwallet "myfile.dat".

I get the following the error when trying to import the wallet: error code: -8 error message: Cannot open wallet dump file.

I have also tried to replace stop the node on server 2 and copy the wallet.dat over to the other server and then start the wallet up again on server 2. I get the following error in the logs: CDBEnv::Open: LogDir=/home/cryptodaemon/.bitcoincash/database ErrorFile=/home/cryptodaemon/.bitcoincash/db.log 2018-09-09 07:48:21 Failed to rename wallet.dat to wallet.dat.1536479301.bak

How can I move the wallet from one server to another? Could anyone give me pointers in doing this?

### Can you reliably reproduce the issue?
#### If so, please list the steps to reproduce below:
1.
2.
3.

### Expected behaviour
Tell us what should happen

The same wallet from server 1 should be replicated on server 2.

### Actual behaviour
Tell us what happens instead

ogDir=/home/cryptodaemon/.bitcoincash/database ErrorFile=/home/cryptodaemon/.bitcoincash/db.log 2018-09-09 07:48:21 Failed to rename wallet.dat to wallet.dat.1536479301.bak

### Screenshots.
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### What version of bitcoin-abc are you using?
List the version number/commit ID, and if it is an official binary, self compiled or a distribution package such as PPA.

### Machine specs:
- OS: debian 8
- CPU: 8, i7
- RAM: 44gb
- Disk size: 1.5tb
- Disk Type (HD/SDD): HD

### Any extra information that might be useful in the debugging process.
This is normally the contents of a `debug.log` or `config.log` file. Raw text or a link to a pastebin type site are preferred.