sqltest: derace TestBackupRestoreBank
sqltest: derace TestBackupRestoreBank

There was a race between setting the testDisableTableLeases knob back to false
and the sql code that uses that value to bypass table leases. This knob reset
happens in a defer that runs after the testcluster's stopper.Stop call returns.
The stopper returning should mean that the server is done, so this behavior is
wrong. #9181 is about fixing this wrongness.

This commit uses a stopper instead of a context to make sure we wait for the
bank goroutine to return before the deferred reset of the table lease knob. This
means no sql queries are being sent, and so none are being executed, avoiding
the race.

Closes #8813.

veteranlu/cockroach,petermattis/cockroach,maxlang/cockroach,glycerine/cockroach,paperstreet/cockroach,veteranlu/cockroach,glycerine/cockroach,petermattis/cockroach,glycerine/cockroach,veteranlu/cockroach,paperstreet/cockroach,maxlang/cockroach,vaibhavarora/cockroach,glycerine/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,cockroachdb/cockroach,veteranlu/cockroach,maxlang/cockroach,petermattis/cockroach,glycerine/cockroach,glycerine/cockroach,paperstreet/cockroach,maxlang/cockroach,veteranlu/cockroach,paperstreet/cockroach,veteranlu/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,petermattis/cockroach,petermattis/cockroach,paperstreet/cockroach,petermattis/cockroach,glycerine/cockroach,veteranlu/cockroach,maxlang/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,maxlang/cockroach,cockroachdb/cockroach,cockroachdb/cockroach,petermattis/cockroach,glycerine/cockroach,cockroachdb/cockroach,cockroachdb/cockroach,maxlang/cockroach,veteranlu/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,maxlang/cockroach,paperstreet/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,petermattis/cockroach,vaibhavarora/cockroach