Players can spawn in and take damage or die before the world loads correctly

Verification builds:
1.10.0.4 Beta
1.9.0

Summary:
Players can spawn into a world and take damage before the world has finished loading, or before the player has fully joined a multiplayer world. This can result in players dying before they are able to move to safety.

Steps to Reproduce:

1. Spawn a zombie
2. Enter survival mode
3. Leave the world
4. Join the world again

Observed Results:
The player rejoins in the middle of an attack, with a different amount of health than from when they last left the world, suggesting that the zombie had free hits on the player.

Expected Results:
Players should not die or take damage before they have fully joined the world.

Screenshots/Videos attached: No

Notes: