HAMMER 61A/Many: Stabilization
* Fix a buffer exhaustion issue. When creating large numbers of empty files
a single inode sync of the directory can exhaust the buffer cache because
not enough other things get dirty enough to force a flush.
Put a check in the record syncing code and do a partial finalization if
necessary to avoid deadlocking the buffer cache.
* Fix a panic caused by a missing call to hammer_cursor_deleted_element().
Reported-by: Michael Neumann <mneumann@ntecs.de>,
Gergo Szakal <bastyaelvtars@gmail.com>