api: fix snasphot-pull

[tbe]

in the API, snapshotPull never finished reading the target repository within the async block. So the target was treated as an empty snapshot, and a pull would only carry over the content from the sources

Fixes #1610

Description of the Change

This PR adds calls LoadComplete on freshToSnapshot.

Checklist

As this is a very minor change, i did not attribute myself in Authors.

• allow Maintainers to edit PR (rebase, run coverage, help with tests, ...)
• unit-test added (if change is algorithm)
• functional test added/updated (if change is functional)
• man page updated (if applicable)
• bash completion updated (if applicable)
• documentation updated
• author name in AUTHORS

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.06%. Comparing base (f59b0d2) to head (f95153a).

Files with missing lines	Patch %	Lines
api/snapshot.go	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1611      +/-   ##
==========================================
- Coverage   77.37%   77.06%   -0.32%     
==========================================
  Files         165      165              
  Lines       15747    15750       +3     
==========================================
- Hits        12185    12137      -48     
- Misses       2356     2410      +54     
+ Partials     1206     1203       -3     

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