multi: ensure link is always torn down due to db failures, add exponential back off for sql-kvdb failures #11341

Job	Run time
check commits	6m 11s
RPC and mobile compilation check	2m 9s
lint code	6m 25s
Sqlc check	22s
cross compilation	48m 26s
check pinned dependencies (google.golang.org/grpc v1.53.0)	5s
check pinned dependencies (github.com/golang/protobuf v1.5.2)	3s
check release notes updated	0s
sample configuration check	36s
run ubuntu itests (btcd, backend=btcd)	49m 31s
run ubuntu itests (bitcoind, backend=bitcoind)	1h 1m 2s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	59m 24s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling")	1h 1m 23s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	1h 19m 40s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 41m 3s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	52m 15s
run ubuntu itests (neutrino, backend=neutrino)	57m 38s
run unit tests (btcd unit-cover)	17m 50s
run unit tests (unit tags="kvdb_etcd")	18m 49s
run unit tests (unit tags="kvdb_postgres")	17m 59s
run unit tests (unit tags="kvdb_sqlite")	16m 41s
run unit tests (btcd unit-race)	3h 46m 46s
run windows itest	40m 37s
	15h 24m 55s

Provide feedback