Optimize callback lookup in event handlers
Optimize callback lookup in event handlers

The event handler code currently invokes PyImport_ImportModule
which is very heavyweight. This is not in fact required, since
we know the libvirt module has already been imported. We can
thus use PyImport_ImportModuleNoBlock and do away with the
global variables caching the imported module reference.

Signed-off-by: Daniel P. Berrange <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

libvirt/libvirt-python,libvirt/libvirt-python,libvirt/libvirt-python