Some vendors insist that floppy images need to be exactly 1440 KiB in
size and have a suffix of ".img". Let's adapt to this and assume that
this doesn't break other vendors.
Closes-Bug: 2100276
Change-Id: I5be6380e8c8c3eac5bea1c189b205b05a9fae625
(cherry picked from commit 56dbf38ed8f200ff91d58559962d9265dff9ee83)
(cherry picked from commit bc565cf543b00f09b980fbbed25023bab8ac6fb4)
1e9877f4a5