Bug 1748014

Description of problem:

Booting the RHEL 8 ISO, if the user hits escape to access the boot prompt, as
happens, for example, when kickstarting from the ISO, long lines will force an
unusual wrap that includes an extra, cosmetic newline. Backspace then redraws
the whole line, but will position the cursor after a phantom space that doesn't
exist in the actual input buffer.

How reproducible:

Boot RHEL 8 ISO in KVM/QEMU, ESC, enter a long command line.


Steps to Reproduce:

1. Boot RHEL 8 ISO.
2. Hit escape prior to automatic boot.
3. Enter this all on one line:

linux 1234567890x1234567890x1234567890x1234567890x1234567890x1234567890x1234567890x1234567890x1234567890

4. On wrap, backspace and note the odd behaviour.
5. Use ^L to refresh the screen, showing that what was displayed was not in fact
the content of the input buffer.

Additional info:

^U and ^L work and can help manipulate and show the actual buffer content. The
customer bringing this issue to us enters longish kickstart sepecifiers and has
been thrown off by the formatting, which introduces errors. There's still
some chance they're seeing actual erroneous input passed through, generated by
the line editor's wrapping bug, but I'm assuming it's purely cosmetic until we
can identify and reproduce a hard error.