job queue: log the opcode error too
job queue: log the opcode error too

Currently we only log "Error in opcode ...", but we don't log the error itself.
This is not good for debugging.

Reviewed-by: ultrotter

bitemyapp/ganeti,bitemyapp/ganeti,apyrgio/snf-ganeti,andir/ganeti,yiannist/ganeti,dimara/ganeti,onponomarev/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti,apyrgio/ganeti,onponomarev/ganeti,mbakke/ganeti,ganeti/ganeti,grnet/snf-ganeti,grnet/snf-ganeti,apyrgio/ganeti,yiannist/ganeti,leshchevds/ganeti,leshchevds/ganeti,apyrgio/snf-ganeti,dimara/ganeti,mbakke/ganeti,andir/ganeti,mbakke/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti,andir/ganeti,leshchevds/ganeti,yiannist/ganeti