Add support for options to 'shareiscsi'.
+ name/iqn	Full iSCSI Qualified Name (IQN), including identifier
		Default: Generated by iscsi_generate_target()
+ lun		LUN (0-16384)
		Default: 0
+ type		Share mode (fileio, blockio, nullio, disk, tape)
		Default: fileio
+ iomode	IO mode (wb, wt, ro)
		Default: wt
+ blocksize	Logical block size (512, 1024, 2048, 4096)
		Default: 512
NOTE: Reshare works, but gives a failure because it do the
      reshare in iscsi_update_shareopts() BUT, for some
      reason, sa_enable_share() is called just after
      iscsi_update_shareopts() have enabled the share!!