When passing LUN IDs through treat ASCII values as fixed-length, not
interpreating NULLs as EOLs, but converting them to spaces.

SPC-4 does not tell that T10-based IDs should be NULL-terminated/padded.
And while it tells that it should include only ASCII chars (0x20-0x7F),
there are some USB sticks (SanDisk Ultra Fit), that have NULLs inside
the value. Treating NULLs as EOLs there made those LUN IDs non-unique.

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