Leads that are hanging Mobs are glitchy and do not appear on fences in SMP

Put the summary of the bug you're having here

*What I expected to happen was...:That the mobs would just Hang there and the lead would work

What actually happened was...:
The lead didn't appear and the mobs just glitched around.

Steps to Reproduce:
1. Use a lead on a mob
2. Hang it on a fence post that's Off the ground
3. Then the mobs should be glitching (only works on SMP