As part of the preparation to the switch interceptor feature, this
function is changed to return error instead of error channel that
is closed automatically.
Returning an error channel has become complex to maintain and
implement when adding more asynchronous flows to the switch.
The change doesn't affect the current behavior which logs the
errors as before.
<time> [ERR] HSWC: ChannelLink(<chan>): unhandled error while forwarding htlc packet over htlcswitch: insufficient bandwidth to route htlc
<time> [ERR] HSWC: ChannelLink(<chan>): unhandled error while forwarding htlc packet over htlcswitch: node configured to disallow forwards
<time> [ERR] HSWC: ChannelLink(<chan>): unhandled error while forwarding htlc packet over htlcswitch: UnknownNextPeer
<time> [ERR] HSWC: ChannelLink(<chan>): Unhandled error while reforwarding htlc settle/fail over htlcswitch: AmountBelowMinimum(amt=<amt>, update=(lnwire.ChannelUpdate) {
<time> [ERR] HSWC: ChannelLink(<chan>): Unhandled error while reforwarding htlc settle/fail over htlcswitch: circuit has already been closed
<time> [ERR] HSWC: ChannelLink(<chan>): Unhandled error while reforwarding htlc settle/fail over htlcswitch: FeeInsufficient(htlc_amt==<amt>, update=(lnwire.ChannelUpdate) {
<time> [ERR] HSWC: ChannelLink(<chan>): Unhandled error while reforwarding htlc settle/fail over htlcswitch: insufficient bandwidth to route htlc
<time> [ERR] HSWC: ChannelLink(<chan>): Unhandled error while reforwarding htlc settle/fail over htlcswitch: node configured to disallow forwards
<time> [ERR] HSWC: ChannelLink(<chan>): Unhandled error while reforwarding htlc settle/fail over htlcswitch: UnknownNextPeer
<time> [ERR] HSWC: ChannelLink(<chan>): failing link: unable to synchronize channel states: unable to send chan sync message for ChannelPoint(<chan_point>): set tcp <ip>: use of closed network connection with error: unable to resume channel, recovery required
<time> [ERR] HSWC: Unhandled error while reforwarding htlc settle/fail over htlcswitch: AmountBelowMinimum(amt=<amt>, update=(lnwire.ChannelUpdate) {
<time> [ERR] HSWC: Unhandled error while reforwarding htlc settle/fail over htlcswitch: circuit has already been closed
<time> [ERR] HSWC: Unhandled error while reforwarding htlc settle/fail over htlcswitch: FeeInsufficient(htlc_amt==<amt>, update=(lnwire.ChannelUpdate) {
<time> [ERR] HSWC: Unhandled error while reforwarding htlc settle/fail over htlcswitch: insufficient bandwidth to route htlc
<time> [ERR] HSWC: Unhandled error while reforwarding htlc settle/fail over htlcswitch: node configured to disallow forwards
<time> [ERR] HSWC: Unhandled error while reforwarding htlc settle/fail over htlcswitch: UnknownNextPeer