breacharbiter: don't watch for channel closes if time locked balance is non-zero
breacharbiter: don't watch for channel closes if time locked balance is non-zero

This commit fixes a slight logic error in the breachArbiter. Previously
we wouldn’t watch a pending channel for closure if the regular
(settled) balance was non-zero. However, this was incorrect, as it’s
possible for us to be on the receiving side of a channel force closure.
This error would leave certain channels as “pending close zombies”
forever until a user manually deleted the entry (or promoted it to be
fully closed).

To fix this, we now utilize the new `TimeLockedBalance` field to make a
better judgment as to if the utxoNursery is watching over a channel or
not.

AndrewSamokhvalov/lnd,ddustin/lnd,aakselrod/lnd,LightningNetwork/lnd,ddustin/lnd,AndrewSamokhvalov/lnd,aakselrod/lnd,LightningNetwork/lnd