routing: fix mc blinded path behaviour. #16840

Job	Run time
RPC and mobile compilation check	2m 46s
lint code	4m 59s
check commits	7m 8s
cross compilation	31m 35s
sample configuration check	1m 29s
Sqlc check	1m 9s
run unit tests (btcd unit-cover)	6m 49s
run macOS itest	49m 54s
check pinned dependencies (google.golang.org/grpc v1.59.0)	4s
run unit tests (unit tags="kvdb_etcd")	20m 49s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	4s
run unit tests (unit tags="kvdb_postgres")	19m 51s
run ubuntu itests (btcd, backend=btcd cover=1)	32m 29s
run unit tests (unit tags="kvdb_sqlite")	18m 49s
run windows itest	7m 36s
run ubuntu itests (bitcoind, backend=bitcoind cover=1)	41m 7s
run unit tests (btcd unit-race)	39m 35s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	39m 33s
run unit tests (unit-module)	1m 2s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling" cover=1)	41m 4s
check release notes updated	3s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	54m 58s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 12m 28s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	42m 23s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	1h 11m 4s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	41m 50s
run ubuntu itests (neutrino, backend=neutrino cover=1)	39m 0s
finish	3s
	11h 29m 41s

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