LU-657 obdfilter: commit pending journals if -ENOSPC

LU-657 obdfilter: commit pending journals if -ENOSPC

in filter_preprw_write, if there is no enough space for this
write operation, then commit the pending journals to get some
more disk space and retry it.

Signed-off-by: Hongchao Zhang <hongchao.zhang@whamcloud.com>
Change-Id: I46106b26443bb203eee6f01a0795b47be09170a6
Reviewed-on: http://review.whamcloud.com/3446
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>