initramfs-uniboot: Set default rootdelay globally, instead of initramfs-module-bootmenu.

initramfs-uniboot: Set default rootdelay globally, instead of initramfs-module-bootmenu.
* That's because otherwise it's half-solution - after kexec, there won't be
delay, and rootfs won't be detected.
* Again, people who don't need and don't want delay, should pass rootdelay=0.