Adds Fedora 24, disables sig checks for 24 since it's rolling

src/fedora.ipxe

@@ -14,6 +14,7 @@ menu Fedora - ${arch} - Image Sig Checks: [${img_sigs_enabled}]
 item 23 ${os} 23
 item 22 ${os} 22
 item 21 ${os} 21
+item 24 ${os} 24 Alpha
 isset ${osversion} || choose osversion || goto linux_menu
 set ova ${os} ${osversion}
 goto product_sku
@@ -25,6 +26,7 @@ item Workstation ${ova} Workstation
 item Cloud_Atomic ${ova} Cloud Atomic
 isset ${sku_type} || choose sku_type || goto fedora
 set dir fedora/releases/${osversion}/${sku_type}/${arch}/os
+iseq ${osversion} 24 && && set mirror mirrors.kernel.org && set dir fedora/releases/test/${osversion}_Alpha/${sku_type}/${arch}/os
 set ova ${ova} ${sku_type}
 echo ${cls}
 goto boottype
@@ -56,6 +58,7 @@ initrd http://${mirror}/${dir}/images/pxeboot/initrd.img
 echo
 echo MD5sums:
 md5sum vmlinuz initrd.img
+iseq ${osversion} 24 && echo skipping signature check for 24 Alpha && goto skip_sigs 
 iseq ${img_sigs_enabled} true && goto verify_sigs || goto skip_sigs
 :verify_sigs
 echo