Scenario risk is using "default" connection on a cluster

Fixes https://bugs.launchpad.net/oq-engine/+bug/1167969
Scenario risk is using "default" connection on a cluster

Changed 'admin' user to 'job_init'
Fixes https://bugs.launchpad.net/oq-engine/+bug/1167969
Merge pull request #1130 from daniviga/fixes-1167969

Scenario risk is using "default" connection on a cluster
[r=micheles] [f=1167969]