iotests: Add creation test to 153

This patch adds a test case to 153 which tries to overwrite an image
(using qemu-img create) while it is in use.  Without the original user
explicitly sharing the necessary permissions (writing and truncation),
this should not be allowed.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20180509215336.31304-4-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
2 files changed