Feature-9904: Enhancing NG-UI to enable Juju operational view dashboard

Added methods in n2vc_juju_conn and libjuju to suppot configs list
and executed actions/history of actions. Added method in n2vc juju conn
to call libjuju methods to get actions, configs and history of actions.

Change-Id: I845789080d148fa42e859dcda185da1e62b4c489
Signed-off-by: ksaikiranr <saikiran.k@tataelxsi.co.in>