[SCSI] Fix leak of Scsi_Cmnds

When a request is deferred in scsi_init_io because the sg table could not
be allocated, the associated scsi_cmnd is not released and the request is
not marked with REQ_DONTPREP.  When the command is retried, if
scsi_prep_fn decides to kill it then the scsi_cmnd will never be released.

This patch (as573) changes scsi_init_io so that it calls scsi_put_command
before deferring a request.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>