qtest: add fuzz test case

qtest: add fuzz test case

Currently the device fuzzer finds more and more issues.
For every fuzz case, we need not only the fixes but also
the corresponding test case. We can analysis the reproducer
for every case and find what happened in where and write
a beautiful test case. However the raw data of reproducer is not
friendly to analysis. It will take a very long time, even far more
than the fixes itself. So let's create a new file to hold all of
the fuzz test cases and just use the raw data to act as the test
case. This way nobody will be afraid of writing a test case for
the fuzz reproducer.

This patch adds the issue LP#1878263 test case.

Signed-off-by: Li Qiang <liq3ea@163.com>
Message-Id: <20200921160605.19329-1-liq3ea@163.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
[thuth: Slightly adjusted commit message, removed empty lines]
Signed-off-by: Thomas Huth <thuth@redhat.com>