increase delay before starting of storage deal

[nonsense]

Storage deals have been flaky with the following error message:

tg-lotus-soup-bu25rsp961nsf8cpnbg0-clients-2 | {"ts":1602510412168376713,"msg":"","group_id":"clients","run_id":"bu25rsp961nsf8cpnbg0","event":{"message_event":{"message":"started storage deal 1 -> bafyreig5amdmziyl2coxfopu5r3qvvobqfkszsk64kbpwim7eyqx4qkilm"}}}
tg-lotus-soup-bu25rsp961nsf8cpnbg0-clients-2 | {"ts":1602510412168487432,"msg":"","group_id":"clients","run_id":"bu25rsp961nsf8cpnbg0","event":{"message_event":{"message":"started storage deal 2 -> bafyreiho3hpcwp5e7nmvl7qyen2uyvkzcxtcrnqup4fjdekbii5jp5aa6m"}}}
tg-lotus-soup-bu25rsp961nsf8cpnbg0-clients-2 | {"ts":1602510412168597837,"msg":"","group_id":"clients","run_id":"bu25rsp961nsf8cpnbg0","event":{"message_event":{"message":"started storage deal 0 -> bafyreierktbi6nrfaidpjlwect4cvgydqsurjr7apyryzvyewtavmiteoe"}}}
tg-lotus-soup-bu25rsp961nsf8cpnbg0-clients-2 | 2020-10-12T13:46:52.184Z ERROR  storagemarket_impl  clientstates/client_states.go:289   deal bafyreiho3hpcwp5e7nmvl7qyen2uyvkzcxtcrnqup4fjdekbii5jp5aa6m failed: unexpected deal status while waiting for data request: 11 (StorageDealFailing). Provider message: deal rejected: clientMarketBalance.Available too small

I am not exactly sure, why increasing the sleep prior to starting a deal helps, but it seems to help. The comment // this to avoid failure to get block makes me think that we need to wait for a few epochs before starting a deal.

[nonsense]

This is actually a bug within the deals functionality of Lotus, so no need to amend the test for now.