Fixed issue with BigQuery jobs for update/upsert failing

[fernst]

Noticed that BQ statements don't support setting the Create Disposition when DML statements are issued

{
  "code" : 400,
  "errors" : [ {
    "domain" : "global",
    "location" : "q",
    "locationType" : "parameter",
    "message" : "Cannot set create disposition in jobs with DML statements",
    "reason" : "invalidQuery"
  } ],
  "message" : "Cannot set create disposition in jobs with DML statements",
  "status" : "INVALID_ARGUMENT"
}