qemu.enospc:update the test.bindir to data_dir.get_data_dir

Now use test.bindir will not find the image file, just update it
to new interface data_dir.get_data_dir

Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
Merge pull request #444 from QiuMike/qemu.enospc_update_the_test.bindir_to_data_dir.get_data_dir

qemu.enospc:update the test.bindir to data_dir.get_data_dir