Detect duplicate queue insert via mysql error number (#440)
Detect duplicate queue insert via mysql error number (#440)

* Detect duplicate queue insert via server error number

* go imports

* Pull out the duplicate check

RJPercival/trillian,daviddrysdale/trillian,AlCutter/trillian,Martin2112/trillian,Martin2112/trillian,google/trillian,RJPercival/trillian,daviddrysdale/trillian,Martin2112/trillian,gdbelvin/trillian,gdbelvin/trillian,gtank/trillian,daviddrysdale/trillian,google/trillian,gdbelvin/trillian,gtank/trillian,codingllama/trillian,codingllama/trillian,AlCutter/trillian