Worker: Accept stake request.

[deepesh-kn]

This is an implementation ticket. The actual implementation may vary as we start working on it.
Please check #5 first for any updates in interface and params.

This function used contract interact to call accept stake request on OSTComposer contract.

• Updates the state in DB. (There is a function that will handle this by passing the state)
  -ACCEPTED if the transaction is successful
  -ACCEPTED_FAILED if the transaction is failed.
• Should wait for n block confirmations.