routing: fix mc blinded path behaviour. #16748

Job	Run time
lint code	4m 31s
cross compilation	31m 11s
check commits	9m 6s
check pinned dependencies (google.golang.org/grpc v1.59.0)	3s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	4s
run macOS itest	51m 36s
check release notes updated	6s
RPC and mobile compilation check	2m 4s
sample configuration check	49s
Sqlc check	2m 38s
run ubuntu itests (btcd, backend=btcd cover=1)	30m 31s
run unit tests (btcd unit-cover)	19m 36s
run ubuntu itests (bitcoind, backend=bitcoind cover=1)	39m 22s
run windows itest	6m 11s
run unit tests (unit tags="kvdb_etcd")	21m 8s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	38m 49s
run unit tests (unit tags="kvdb_postgres")	19m 42s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling" cover=1)	39m 20s
run unit tests (unit tags="kvdb_sqlite")	19m 27s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	54m 4s
run unit tests (btcd unit-race)	40m 17s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 11m 35s
run unit tests (unit-module)	1m 15s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	42m 33s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	1h 9m 54s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	41m 12s
run ubuntu itests (neutrino, backend=neutrino cover=1)	37m 4s
finish	7s
	11h 34m 15s

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