Don't release volume handle prematurely
Don't release volume handle prematurely

(cherry picked from commit fe263cf66586ea6ba51840b33a00c742b826e207)

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