Add parameter to lassie to indicate if the original request was for a block or car

[willscott]

lassie per https://github.com/filecoin-project/lassie/issues/169 will support a limit= parameter on requests.

• in cases where the request was for a single block (where response blocks are currently cached by the l1) - the parameter limit=10 should be appended to the request made to lassie
• In cases where the request is for a car that is passed on to lassie, the parameter limit=0 should be appended to the request made to lassie

[hannahhoward]

done