iotests: Add copyright line in qcow2.py

iotests: Add copyright line in qcow2.py

The file qcow2.py was originally contributed in 2012 by Kevin Wolf,
but was not given traditional boilerplate headers at the time.  The
missing license was just rectified (commit 16306a7b39) using the
project-default GPLv2+, but as Vladimir is not at Red Hat, he did not
add a Copyright line.  All earlier contributions have come from CC'd
authors, where all but Stefan used a Red Hat address at the time of
the contribution, and that copyright carries over to the split to
qcow2_format.py (d5262c7124).

CC: Kevin Wolf <kwolf@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Eduardo Habkost <ehabkost@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Philippe Mathieu-Daudé <philmd@redhat.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200609205944.3549240-1-eblake@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>