Enable bash tab completion

• Contrail-db-explorer uses argcomplete for bash command tab completion.
• Note that you should start a new shell after running activate-global-python-argcomplete

root@aio51:~# pip install argcomplete
Downloading/unpacking argcomplete
  Downloading argcomplete-1.9.4-py2.py3-none-any.whl
Installing collected packages: argcomplete
Successfully installed argcomplete
Cleaning up...

root@aio51:~# activate-global-python-argcomplete
Installing bash completion script /etc/bash_completion.d/python-argcomplete.sh

root@aio51:~# exit

root@aio51:~# ./db_explorer.py show config_db uuid --type 
access_control_list           domain                        interface_route_table         project                       security_group                virtual_machine_interface
analytics_node                floating_ip                   loadbalancer_member           qos_config                    service_appliance             virtual_network
api_access_list               floating_ip_pool              loadbalancer_pool             qos_forwarding_class          service_appliance_set         virtual_router
bgp_as_a_service              forwarding_class              logical_router                qos_queue                     service_health_check          
bgp_router                    global_qos_config             namespace                     route_table                   service_instance              
config_node                   global_system_config          network_ipam                  route_target                  service_template              
database_node                 global_vrouter_config         network_policy                routing_instance              virtual_ip                    
discovery_service_assignment  instance_ip                   port_tuple                    routing_policy                virtual_machine

---

Reference: argcomplete