sbin/hammer: Remove irrelevant if(S_ISLNK()) case
- Remove if(S_ISLNK()) case for hammer snap since it never matches.
- Also note it shouldn't be matching S_ISLNK() in the first place.
If it does match hammer snap|snaplo|snapq commands will remove
a symlink to the existing snapshot and relink to the new snapshot
which results losing a reference to the old snapshot (although
the old snapshot is still accessible as HAMMER's snapshot is just
a pointer to the filesystem as of certain tid that is resolved
when accessed).