On some platforms after the initramfs init scripts have mounted the root device its
block device disapear from /dev. The union-mount script therefore can't mount the
root device over the aufs. If this case happen, issue a rescan of the devices to
repopulate the /dev filesystem.
This commit will convert the existing file system of flash drive on Arista switches from VFAT to EXT4 in the booting of SONiC. It will take the whole flash and therefore remove the recovery partition. There is a check in the script making sure that the conversion operation will not happen on a non-Arista switch or if the existing file system is not VFAT.
