storage: deflake TestRefreshPendingCommands
storage: deflake TestRefreshPendingCommands

Node liveness heartbeats were causing a range lease to be reacquired
when the test was waiting for them to be drained. Due to the manual
clock, the draining would never properly complete.

Fixes #11771

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