Use workerpool in master daemon
Use workerpool in master daemon

Reusing threads instead of starting one for each request is more efficient.

Reviewed-by: iustinp


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