Move SSH option building into a function
Move SSH option building into a function

I'm going to add another option and it would make maintaining
them in constants even more complicated.

Reviewed-by: ultrotter


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