TestSwapState_ClaimRelayer_ETH test is flaky
This test is failing with some frequency even outside of CI:
```
=== RUN   TestSwapState_ClaimRelayer_ETH
    claim_test.go:147: gas cost to deploy Forwarder.sol: 1998934
    claim_test.go:153: gas cost to call RegisterDomainSeparator: 50391
    claim_test.go:163: gas cost to deploy SwapFactory.sol: 2075776
    claim_test.go:188: gas cost to call new_swap: 53007
    claim_test.go:219: gas cost to call SetReady: 33660
    claim_test.go:239: 
        >-------Error Trace:>---/home/dh/dev/atomic-swap/protocol/xmrmaker/claim_test.go:239
        >-------            >--->------->------->-------/home/dh/dev/atomic-swap/protocol/xmrmaker/claim_test.go:115
        >-------Error:      >---Received unexpected error:
        >-------            >---failed to submit transaction to relayer: message=read tcp 127.0.0.1:42754->127.0.0.1:8545: i/o timeout; code=-32000; data=map[]
        >-------Test:       >---TestSwapState_ClaimRelayer_ETH
--- FAIL: TestSwapState_ClaimRelayer_ETH (401.07s)
```