The parameter 'params' is useless for virDomainGetBlockIoTune API,
and the return value type should be a virTypedParameterPtr but not
integer. And "PyArg_ParseTuple" in functions
libvirt_virDomain{Set,Get}BlockIoTune misses format unit for "format"
argument.

* libvirt-override-api.xml: Remove useless the parameter 'params'
from virDomainGetBlockIoTune API, and change return value type from
integer to virTypedParameterPtr.

* python/libvirt-override.c: Add the missed format units.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=770683Signed-off-by: NAlex Jia <ajia@redhat.com>