fix(vultr): update incorrect ipxe flags
fix(vultr): update incorrect ipxe flags

jonboulle/docs,hkjn/docs-1,iankronquist/docs,joshix/docs,jdloft/docs,coreos/docs,skynet/docs,bq-xiao/docs,ionave/docs,michelleN/docs,ksmaheshkumar/docs-2,endocode/coreos-docs,wli6/docs,mjg59/docs,mischief/coreos-docs,marineam/coreos-docs,atxwebs/docs,robszumski/docs