on the assumption that the unit linked with the device is invariant but
that can change when calling devclass_alloc_unit() (because -1 is passed
or, more simply, because the unit choosen is beyond the table limits).
This results in a completely bogus string building.
Fix this by reserving the necessary room for all the possible characters
printable by a positive integer (we do not allow for negative unit
number).
Reported by: Sandvine Incorporated
Reviewed by: emaste
Sponsored by: Sandvine Incorporated
MFC: 1 week
023c800576