kedifa: Test stabilizing fixup, wait a bit longer on the cauase first start

This implmentation was inspired by the cauase test itself in here: https://lab.nexedi.com/nexedi/caucase/blob/5d8b9602b423ac4831f36a693ffa5cec0af906db/caucase/test.py#L645-656

The test suite was passed. https://nexedijs.erp5.net/#/test_result_module/20211002-11914B25D