vout parameter check in createrawtransaction is confused with missing & type_error.

Summary:
vout parameter in createrawtransaction could be missing or non-num,
but the code simply check the type of vout and throws missing error, which is
not right for string vout.

Test Plan: make check

Reviewers: #bitcoin_abc, O1 Bitcoin ABC, jasonbcox, schancel

Reviewed By: #bitcoin_abc, O1 Bitcoin ABC, jasonbcox, schancel

Subscribers: schancel, jasonbcox, deadalnix, teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1556