pay routes to wrong place ignoring route hint after single failure

[rustyrussell]

Running #3857

$ ./devtools/bolt11-cli decode lnbc10u1p03vu67dqswf6hxareta68w6t5cqzgapp5xd97fyyuu4rqdhh8m3r0nz8udrvap4nc57mcw6005ep93m5mg3rqxqyz5vprzjqv2ylnrne6jp5qpt9pjlnqvs4wgwfl6c5t8zf5u8pag8jzq7g2fz6q20rkqp7jyrfuqqqqlgqqqq86qqjqgwpnqdmzck7sfqad0mz2239v9rzvg2dhmauqy52426kgmhd8cdq3qg70mkcg74w68sfqfvpre0qs53quftry5f9zg5ruz25v2kps9dqquh9zn6
currency: bc
timestamp: 1595306846 (Tue Jul 21 14:17:26 2020)
expiry: 86401 (Wed Jul 22 14:17:27 2020)
payee: 024c78a1ea66e3866bf5e7db5b7c0630435e965f72b7f82d16bae74b6059bdf379
payment_hash: 334be4909ce54606dee7dc46f988fc68d9d0d678a7b78769efa64258ee9b4446
min_final_cltv_expiry: 285
msatoshi: 1000000
amount_msat: 1000000msat
description: 'rusty_twit'
route: (node/chanid/fee/expirydelta)  03144fcc73cea41a002b2865f98190ab90e4ff58a2ce24d3870f5079081e42922d/85789x8396616x33615/1000/1000/144
signature: 304402204383303762c5bd0483ad7ec4a544ac28c4c429b7df7802515556ac8ddda7c34102201023cfddb08f55da3c1204b023cbc10a441c4ac64a24a24507c12a8c558302b4

We get a temporary channel failure, then ignroe route hint:

2020-07-21T06:36:29.665Z DEBUG plugin-pay: Added a channel hint for 613373x582x1/0: enabled true, estimated capacity 751500msat
2020-07-21T06:36:29.665Z INFO plugin-pay: failed: WIRE_TEMPORARY_CHANNEL_FAILURE (reply from remote)
2020-07-21T06:36:29.665Z DEBUG plugin-pay: Retrying 334be4909ce54606dee7dc46f988fc68d9d0d678a7b78769efa64258ee9b4446/0 (1000000msat), new partid 1. 9 attempts left\n
2020-07-21T06:36:29.666Z DEBUG 02ad6fb8d693dc1e4569bcedefadf5f72a931ae027dc0f0c544b34c1c6f3b9a02b-channeld-chan#18450: ... , awaiting 1122
2020-07-21T06:36:29.666Z DEBUG 02ad6fb8d693dc1e4569bcedefadf5f72a931ae027dc0f0c544b34c1c6f3b9a02b-channeld-chan#18450: Got it!
2020-07-21T06:36:29.666Z DEBUG 02ad6fb8d693dc1e4569bcedefadf5f72a931ae027dc0f0c544b34c1c6f3b9a02b-channeld-chan#18450: revoke_and_ack REMOTE: remote_per_commit = 03f921a1eba04ccbd3cb052cb7f1ab2a31ff61f0a05eb555368526c8bf8f33d8cc, old_remote_per_commit = 038feaef13b9f9dd240d96306990a3938f3da2a79864c8ef3acf646edc19810ff3
2020-07-21T06:36:29.666Z DEBUG 02ad6fb8d693dc1e4569bcedefadf5f72a931ae027dc0f0c544b34c1c6f3b9a02b-channeld-chan#18450: Trying commit
2020-07-21T06:36:29.666Z DEBUG 02ad6fb8d693dc1e4569bcedefadf5f72a931ae027dc0f0c544b34c1c6f3b9a02b-channeld-chan#18450: Can't send commit: nothing to send
2020-07-21T06:36:29.667Z DEBUG gossipd: Trying to find a route from (me) to 024c78a1ea66e3866bf5e7db5b7c0630435e965f72b7f82d16bae74b6059bdf379 for 1000000msat
2020-07-21T06:36:29.667Z INFO gossipd: find_route: cannot find 024c78a1ea66e3866bf5e7db5b7c0630435e965f72b7f82d16bae74b6059bdf379
2020-07-21T06:36:29.667Z DEBUG gossipd: REPLY WIRE_GOSSIP_GETROUTE_REPLY with 0 fds
2020-07-21T06:36:29.667Z INFO plugin-pay: Error computing a route to 024c78a1ea66e3866bf5e7db5b7c0630435e965f72b7f82d16bae74b6059bdf379: \"Could not find a route\" (205)