Fix nonce issue for replay attack

[summerpro]

Closes: cosmos/ethermint#687

• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md

• Reviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge PR #XYZ: [title]" (coding standards)

[codecov-io]

Codecov Report

Merging #544 (1be8fd3) into dev (f433c50) will not change coverage.
The diff coverage is 20.00%.

@@           Coverage Diff           @@
##              dev     #544   +/-   ##
=======================================
  Coverage   68.17%   68.17%           
=======================================
  Files         303      303           
  Lines       18370    18370           
=======================================
  Hits        12523    12523           
  Misses       5131     5131           
  Partials      716      716           

Impacted Files	Coverage Δ
app/rpc/namespaces/eth/api.go	0.00% <0.00%> (ø)
app/ante/eth.go	58.90% <100.00%> (ø)

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