BUGFIX - Issue #361 - RHEL6 bootproto=static is no longer an option

Just changing the default to be BOOTPROTO=none for any static
interface, if that doesn't work for older RHEL based distros it
can be modified somewhat easily by any user
BUGFIX - Issue #425 - setting system to memtest image fails
Merge branch 'release24' of git://github.com/cobbler/cobbler into release24
BUGFIX - Issue #386 - gracefully handle kickstart render failures