Reuse the luxi client in cli.SubmitOpCode
Reuse the luxi client in cli.SubmitOpCode

By a mistake, we don't reuse the luxi client. As such, we open and close
the connection at each poll cycle and spam the server logs.

Reviewed-by: ultrotter

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