Fix blobber compilation for conductor tests

[fabioDMFerreira]

Make writemarker and hashnode functions available to the integration tests bundle.

While running conductor tests we are getting next errors because the functions referred to are in a file that is not compiled on conductor tests.

Error: ../blobbercore/handler/handler.go:81:64: undefined: LockWriteMarker
Error: ../blobbercore/handler/handler.go:82:77: undefined: UnlockWriteMarker
Error: ../blobbercore/handler/handler.go:84:61: undefined: LoadRootHashnode

[cnlangzi]

@fabioDMFerreira please fix ci errors first

[codecov-commenter]

Codecov Report

Merging #735 (e578113) into staging (784fb36) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           staging     #735   +/-   ##
========================================
  Coverage    24.15%   24.15%           
========================================
  Files           69       69           
  Lines         7913     7913           
========================================
  Hits          1911     1911           
  Misses        5718     5718           
  Partials       284      284           

Flag	Coverage Δ
Unit-Tests	24.15% <ø> (ø)

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Impacted Files	Coverage Δ
...0chain.net/blobbercore/handler/handler_hashnode.go	57.14% <ø> (ø)
...ain.net/blobbercore/handler/handler_writemarker.go	64.70% <ø> (ø)

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