storage: speed up multiTestContext gossipping
storage: speed up multiTestContext gossipping

Changed multiTestContext.addStore to only add a gossip resolver for the
first store rather than all previous stores. The former behavior could
sometimes lead to delays in initial gossipping of crucial information
such as the system config.

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