While the gamerule mobGriefing is set to false, farmer villagers will not farm crops. Attatched video shows example.

What I expected to happen was...:
Farmers to actively farm crops while mobGriefing was set to false.

What actually happened was...:
After several minutes, no farming occurred while mobGriefing was set to false. Upon setting mobGriefing to true, farming resumed as normal.

Steps to reproduce:
1. Set /gamerule mobGriefing false
2. Find a village and wait near farm, or create farm and spawn farmer
3. Determine that no farming is ever going to happen
4. Set /gamerule mobGriefing true
5. See farming happen almost immediately.