The output from the SCSI inquiry command uses fixed-length space-padded
strings, which are copied into null-terminated strings before use.

This is currently done using strncpy(), with the count parameter set to
the string's fixed length. Because a null terminator is not encountered
in the input, strncpy() does not write one in the output, and GCC warns
about potential string truncation. A null terminator is added manually,
but this is error prone (as shown by the fix for the microtek backend).

Use snprintf() instead, which guarantees a null-terminated result and
resolves the warnings from GCC.