fix(meta): create dentry concurrency cause orphan inodes

[sjp00556]

Motivation

when concurrency create dentries with same parent and name will cause orphan inodes.

Modifications

when create dentry with same parent and name:

• if inodes are same, it will return status OpOk to client, we can treat it as successful (fixed here: f55846a)
• if inodes are not same, it will return proto.OpExistErr

so when we get OpExistErr, it means dentry must create failed, so we should unlink this inode to avoid orphan inode

Types of changes

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Bugfix (non-breaking change which fixes an issue)
• Documentation Update (if none of the other choices apply)
• So on...

Verifying this change

• Make sure that the change passes the testing checks.

This change is already covered by existing tests, such as (please describe tests).

Does this pull request potentially affect one of the following parts:

• Master
• MetaNode
• DataNode
• ObjectNode
• AuthNode
• LcNode
• Blobstore
• Client
• Cli
• SDK
• Other Tools
• Common Packages
• Dependencies
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Review Expection

• in-two-days
• weeks
• free-time
• whenever

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 41.94%. Comparing base (bdffd66) to head (86696fc).
Report is 16 commits behind head on master.

❗ Current head 86696fc differs from pull request most recent head 03de9a9. Consider uploading reports for the commit 03de9a9 to get more accurate results

Files	Patch %	Lines
sdk/meta/api.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3233      +/-   ##
==========================================
+ Coverage   40.49%   41.94%   +1.44%     
==========================================
  Files         603      580      -23     
  Lines      125057   119697    -5360     
==========================================
- Hits        50643    50201     -442     
+ Misses      70051    65187    -4864     
+ Partials     4363     4309      -54     

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