'Appends process_id of instance to cache.
This method will store the pid of a process in cache as
a key: value pair which will be used to kill the process if it
is running while deleting the instance. Instance uuid is used as
a key in the cache and pid will be the value.
:param instance: Object of instance
:param pid: Id of the process'

def add_job(self, instance, pid):

    self.jobs[instance.uuid].append(pid)
