Create stash dir recursively.

When applying an OTA package onto the device in OTA mode,
if the recovery logs haven't been viewed, there is a chance
that /cache/recovery does not exist. Then, stash creation will
fail. Create stash directories recursively to avoid this error.

Test: without /cache/recovery, sideload the OTA on cuttlefish
Change-Id: I5cc01a067d866476a3594e795dcb5b15649e817b