The test_qmp_oob test case calls mkfifo() which does not exist on
win32. Exclude it.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220925113032.1949844-31-bmeng.cn@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>