prepare-sdcard.yaml results in "Firmware Not Found" error

[darthlukan]

The current iteration of the prepare-sdcard.yaml playbook results in an sdcard that will not boot due to a "Firmware Not Found" error in the pi bootloader. The workaround for this is as follows:

1. Manually mount the sdcard EFI partition
2. Run the rsync command manually based on this documentation
3. Unmount the sdcard
4. Expand the 4th (root) partition of the sdcard via parted/gparted/fdisk

Placing the steps into a shell script results in the same behavior, a failed SDCARD and the result is always the same: An error of "special device mmcblk0 not found" or "/dev/mmcblk0p2 is not mounted". Adding "sleep 10" to the script SOMETIMES is enough for the script to be successful, which means we've got to slow things down in order for the filesystem and the kernel to catch up.