Add utils.log_task_wrapper() method

This wrapper add before and after method excecution logs messages:

params = {'task': self.task['uuid'], 'msg': msg % kw}

Log _("Task %(task)s start: %(msg)s") % params
Exectue your method
Log _("Task %(task)s finish: %(msg)s) % params

bp logging

Change-Id: Ib07fe5cfd00637c14010cfe5f49cae9fe55f5eaf