iscsictl.8: Add missing flag parameters

• Add missing parameters to flags in the description of available options.
• Remove spaces between alternative parameters and "|".
• Align descriptions of options to the longest option.
• Use em dash instead of a hyphen.

Reviewed by: bcr
Approved by: doc (bcr)
Approved by: krion (mentor, implicit), mat (mentor, implicit)
Differential Revision: https://reviews.freebsd.org/D18608