sbin/hammer: Remove irrelevant if(S_ISLNK()) case

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).