Increase grub timeout

[Alexander Boström]

My home server was running Fedora 10 and I tried to preupgrade it to
F12, however the F12 kernel wouldn't work at all on this machine (it
oopsed before even mounting the root) and no matter how frantically I
pressed the arrow keys during boot I could never get into the GRUB menu
and stop it from booting into F12 anaconda. Also, it had no CD drive and
LiveUSB boot failed too. Luckily I had another harddrive laying around
which had grub on it, so I could install and boot from that instead and
return to F10. (The real fix turned out to be to upgrade the BIOS.)

Long story short: There are situations where a grub menu is vital, like
until you've successfully booted a new kernel.

/Alexander