storage: make send_multi fully work in parallel.
storage: make send_multi fully work in parallel.

tscholl2/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,DrXyzzy/smc,DrXyzzy/smc,sagemathinc/smc,DrXyzzy/smc,tscholl2/smc,sagemathinc/smc,tscholl2/smc,sagemathinc/smc,tscholl2/smc