routing: fix mc blinded path behaviour. #16834

Job	Run time
Sqlc check	1m 24s
lint code	11m 53s
check commits	7m 17s
RPC and mobile compilation check	2m 39s
check pinned dependencies (google.golang.org/grpc v1.59.0)	6s
sample configuration check	1m 26s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	5s
run ubuntu itests (btcd, backend=btcd cover=1)	32m 29s
run unit tests (btcd unit-cover)	19m 7s
run ubuntu itests (bitcoind, backend=bitcoind cover=1)	41m 18s
cross compilation	31m 3s
run unit tests (unit tags="kvdb_etcd")	21m 8s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	40m 46s
run unit tests (unit tags="kvdb_postgres")	20m 1s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling" cover=1)	42m 11s
run windows itest	6m 15s
run unit tests (unit tags="kvdb_sqlite")	18m 55s
run unit tests (btcd unit-race)	40m 27s
run unit tests (unit-module)	1m 13s
run macOS itest	50m 18s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	53m 50s
check release notes updated	4s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 12m 52s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	41m 48s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	1h 11m 0s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	43m 5s
run ubuntu itests (neutrino, backend=neutrino cover=1)	39m 3s
finish	6s
	11h 51m 49s

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