wgengine/wgcfg: don't send UAPI to disable keep-alives on new peers

That's already the default. Avoid the overhead of writing it on one
side and reading it on the other to do nothing.

Updates #cleanup (noticed while researching something else)

Change-Id: I449c88a022271afb9be5da876bfaf438fe5d3f58
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f