Ubuntu Server 14.04.1 LTS - unable to boot degraded RAID 1 boot disk

Replication - also within a VM

install new Ubuntu Server with RAID1 boot disk

( I used Ubuntu_14.0.4.1_LTS_trusty-server-amd64.iso ).

I have testet with MBR Table ( not with GTP), only two prim partions, md0 --> /boot and / (ext4) , md1 --> swap

a) if you disconnect 2nd Disk in the RAID1 and want to boot the degraded MD a second time ( first boot works!)

or ( more easily )

b) Install Ubuntu Server with RAID1 boot disk and use only 1 disk and boot ( /boot and / on the same partion)

in both cases booting stops with (initramfs) prompt, error ( mount /root ... - Device or Resource busy )

Workaround: add a "sleep 2" in /etc/initramfs/scripts/local-premount/delay.sh & update-initramfs -u

It seams that the MD device is not ready for mounting as a root partion. Waiting for the disk device(s) is needed. if
you have both disks in the RAID1 up booting never fails

similar Situation is also described in

http://ubuntuforums.org/showthread.php?t=2241430&goto=newpost
with same workaround