check prev nonce for rollback wm

[Hitenjain14]

Changes

Fixes

Tests

Tasks to complete before merging PR:

• [ ] Ensure system tests are passing. If not Run them manually to check for any regressions :clipboard:
• [ ] Do any new system tests need added to test this change? do any existing system tests need updated? If so create a PR at 0chain/system_test
• [ ] Merge your system tests PR to master AFTER merging this PR

Associated PRs (Link as appropriate):

• 0chain:
• gosdk:
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...

[codecov-commenter]

Codecov Report

Attention: 29 lines in your changes are missing coverage. Please review.

Comparison is base (21a5976) 23.63% compared to head (a28e8f0) 23.57%.

Files	Patch %	Lines
.../go/0chain.net/blobbercore/writemarker/protocol.go	0.00%	16 Missing :warning:
...de/go/0chain.net/blobbercore/writemarker/entity.go	0.00%	13 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## staging #1369 +/- ## =========================================== - Coverage 23.63% 23.57% -0.07% =========================================== Files 87 87 Lines 10098 10124 +26 =========================================== Hits 2387 2387 - Misses 7415 7441 +26 Partials 296 296 ``` | [Flag](https://app.codecov.io/gh/0chain/blobber/pull/1369/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=0chain) | Coverage Δ | | |---|---|---| | [Unit-Tests](https://app.codecov.io/gh/0chain/blobber/pull/1369/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=0chain) | `23.57% <0.00%> (-0.07%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=0chain#carryforward-flags-in-the-pull-request-comment) to find out more.

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