kvm: fix bytes_read

[Wenzel]

KVM driver read_physical: bytes_read value was not updated correctly

[codecov-commenter]

Codecov Report

Merging #210 (df02882) into master (82a329e) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master     #210   +/-   ##
=======================================
  Coverage   16.06%   16.06%           
=======================================
  Files          10       10           
  Lines         579      579           
  Branches       87       87           
=======================================
  Hits           93       93           
  Misses        468      468           
  Partials       18       18           

Flag	Coverage Δ
unittests	16.06% <0.00%> (ø)

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Impacted Files	Coverage Δ
src/driver/kvm.rs	28.57% <0.00%> (ø)

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[rageagainsthepc]

This would have been a good opportunity to add some unit tests which make sure that bytes_read is updated correctly. 😛

[Wenzel]

I agree, with first integration tests are what yields most value here