Implement small KPI to access LUN options instead doing it by hands.

MFC after:	2 weeks

(cherry picked from commit bca290815a962a134e3c1f1f17a9870a0191ef75)
Remove non-functional remnants of control LUN -- 18MB of RAM for nothing.

(cherry picked from commit cc4256abf80c0815a7e57bba6f89d58dae14ecaf)
Add "vendor", "product" and "revision" options to control inquiry data.

MFC after:	2 weeks

(cherry picked from commit b9b3039f44e806474252bd6bd814b76ab493916d)
Respect "vendor" option in all places.

MFC after:	2 weeks

(cherry picked from commit 545a63211e99ca3442fd793c3ae6000d41ca5c90)
Remove custom processing for "file" option.

(cherry picked from commit c9c00ba71dc1483518757193d6510e38a1de255b)
Format Portal Group Tag same as istgt does -- %4.4x instead of %x.

SPC-4 spec tells it should be "two or more hexadecimal digits".
RFC3720 tells it is 16-bit value.

MFC after:	2 weeks

(cherry picked from commit d0cff5099e094ba6bc76e9a9fbdbfd6fd4fdf5d6)
Document additional LUN/backend options.

(cherry picked from commit dee1ee5f2ca43aa981a04316d6437fd33404ee50)