Correct flushing when sending full file
Correct flushing when sending full file

(cherry picked from commit 243ee5bad46c276b207e1d253898e60c97700916)

uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend