Steps to reproduce in creative:

1. Place fence post
2. Spawn wolf with spawn egg
3. Tame wolf with bone
4. Use lead to attach wolf to post
5. Right-click fence post (or move fence post using a piston) to release wolf
6. Spawn cow
7. Attack cow with empty hand

Expected behavior:

  Wolf attacks cow, and follows the cow if/when it runs away.

Observed behavior:

   Wolf will not attack the cow unless it is within the region the wolf could reach while leashed.

   Also, the wolf will not wander from that area, but can follow the player via teleportation.