LU-325 using preallocated objects if OST has enough disk space

LU-325 using preallocated objects if OST has enough disk space

during creating files, if ENOSPC is returned by one OST, the preallocated
objects in the corresponding OSC should still can be used if there is enough
blocks but no inode available in the OST.

Change-Id: I9d57461698d1c0fb3a492188fb4ce1519d65efc7
Signed-off-by: Hongchao Zhang <hongchao.zhang@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1051
Tested-by: Hudson
Reviewed-by: Johann Lombardi <johann@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>