sesutil: plug memory leaks

[asomers]

Summary

MFC after: 2 weeks
Sponsored by: Axcient

Test Plan

ran all sesutil commands with valgrind

[mav]

I have no objections, but have few comments.

usr.sbin/sesutil/sesutil.c

528

I usually prefer to free resources in order opposite to allocation.

It is also a bit weird to allocate/free memory on every loop iteration. I have some enclosures with about 300 elements.

639

As I see fetch_device_details() always initializes model and serial arguments, even in case of error, so this was not necessary. Though it is not wrong either. As you wish.

856

Same comment about every iteration.

[asomers]

I sort of forgot about this review. I've committed it as-is, and next I'll make the memory allocations more efficient, as @mav suggested.