fix: Added clear to dictionary OverrideToNetworkPrefab in NetworkManager Initialize

[jordruss]

Added clear to dictionary OverrideToNetworkPrefab in NetworkManager Initialize. This should be cleared with NetworkPrefabOverrideLinks to rebuild on each connect.

Network prefabs are added to OverrideToNetworkPrefab with each connection. From the rest of the logic presented OverrideToNetworkPrefab should be cleared in Initialize before the override dictionaries are built. Without this change on second connections onwards errors trigger indicating a Network Prefab has been added multiple times and Network Prefabs with overrides do not spawn on clients.

To replicate add an override to a NetworkPrefab in NetworkManager and attempt multiple connections.

[unity-cla-assistant]

All committers have signed the CLA.

[LukeStampfli]

The CLA assistant is not passing here because you made a commit from an email which is not linked to a Github account. You'd have to amend the commit and change the author email.

[NoelStephensUnity]

This is a good addition.

[NoelStephensUnity]

Hi @jordanvr,
This was a good catch and will be updated in the next patch.
The fix is implemented in PR-1508.
Thank you for your submission!

[0xFA11]

thanks for the review Noel
we should pull author's branch and push it to our repo to give them credit in the git history/commits.
I'll take care of that, until then, I'll reopen this PR and assign it to myself.