support graceful exit for watchdb

[lcmmhcc]

• 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

---

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-commenter]

Codecov Report

Merging #2441 (02301e1) into dev (533cfc3) will decrease coverage by 2.67%. The diff coverage is n/a.

:exclamation: Current head 02301e1 differs from pull request most recent head 0581d50. Consider uploading reports for the commit 0581d50 to get more accurate results

@@            Coverage Diff             @@
##              dev    #2441      +/-   ##
==========================================
- Coverage   34.41%   31.73%   -2.68%     
==========================================
  Files         343       51     -292     
  Lines       39192     4887   -34305     
==========================================
- Hits        13488     1551   -11937     
+ Misses      24693     3182   -21511     
+ Partials     1011      154     -857     

Impacted Files	Coverage Δ
x/evm/watcher/watcher.go
x/wasm/keeper/handler_plugin.go
x/erc20/genesis.go
x/staking/types/address.go
x/evm/watcher/codec.go
x/distribution/types/params.go
x/wasm/handler.go
x/evm/module.go
x/staking/keeper/val_state.go
x/distribution/abci.go
... and 282 more

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