add blocks to the blockstore before returning them from blockservice sessions.
add blocks to the blockstore before returning them from blockservice sessions.

fixes #4062 (yay!)

License: MIT
Signed-off-by: Steven Allen <4068f0880b399410602d694b3cc711c8a8f4727e@stebalien.com>

ianopolous/go-ipfs,chriscool/go-ipfs,Luzifer/go-ipfs,OpenBazaar/go-ipfs,ianopolous/go-ipfs,MichaelMure/go-ipfs,chriscool/go-ipfs,kyledrake/go-ipfs,chriscool/go-ipfs,kyledrake/go-ipfs,WilliButz/go-ipfs,WilliButz/go-ipfs,Quantomicus/go-ipfs,Quantomicus/go-ipfs,Luzifer/go-ipfs,WilliButz/go-ipfs,kyledrake/go-ipfs,Luzifer/go-ipfs,MichaelMure/go-ipfs,ianopolous/go-ipfs,MichaelMure/go-ipfs,OpenBazaar/go-ipfs,OpenBazaar/go-ipfs,Quantomicus/go-ipfs