updates tailscale/corp#32600
A localAPI/cli call to reload-config can end up leaving magicsock's mutex
locked. We were missing an unlock for the early exit where there's no change in
the static endpoints when the disk-based config is loaded. This is not likely
the root cause of the linked issue - just noted during investigation.
Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>