Description of problem:

Currently overcloudrc sets no_proxy environment parameter, while stackrc doesn't.

This means that if an operator run
 $ source ~/overcloudrc
 $ source ~/stackrc
no_proxy parameter is not unset by stackrc and keeps vip ips.

If an operator updates overcloud with commands like 'openstack overcloud deploy' then,
the command is executed with no_proxy parameter set.
The command generates overcloudrc with combining current no_proxy parameter and overcloud vips,
it ends up in putting duplicated ips in overcloudrc.

~~~
(undercloud) [stack@undercloud-0 ~]$ openstack stack list
+--------------------------------------+------------+----------------------------------+-----------------+----------------------+--------------+
| ID                                   | Stack Name | Project                          | Stack Status    | Creation Time        | Updated Time |
+--------------------------------------+------------+----------------------------------+-----------------+----------------------+--------------+
| 0aed599e-1463-4951-b2c8-86fdd84f8445 | overcloud  | 16d31b5c4e284a7e8ae6f842d8ab228d | CREATE_COMPLETE | 2020-04-01T01:08:05Z | None         |
+--------------------------------------+------------+----------------------------------+-----------------+----------------------+--------------+
(undercloud) [stack@undercloud-0 ~]$ openstack port list | egrep -e 10.0.0.124 -e 192.168.24.8
| 1178fbda-2d3c-4f47-b77c-45f976ba59ad | control_virtual_ip      | fa:16:3e:7f:72:10 | ip_address='192.168.24.8', subnet_id='38bf9304-f15d-49b2-891d-aba9ae54f521'  | DOWN   |
| 58155b41-802d-4b9b-810b-bef9443e372d | public_virtual_ip       | fa:16:3e:37:ba:39 | ip_address='10.0.0.124', subnet_id='3f719ed1-4746-4358-a6aa-44b6a78251dc'    | DOWN   |
(undercloud) [stack@undercloud-0 ~]$ cat overcloudrc 
# Clear any old environment that may conflict.
for key in $( set | awk '{FS="="}  /^OS_/ {print $1}' ); do unset $key ; done
export OS_NO_CACHE=True
export COMPUTE_API_VERSION=1.1
export OS_USERNAME=admin
export no_proxy=,10.0.0.124,192.168.24.8 <==========(*)
export OS_REGION_NAME=regionOne
export OS_USER_DOMAIN_NAME=Default
export OS_VOLUME_API_VERSION=3
export OS_CLOUDNAME=overcloud
export OS_AUTH_URL=http://10.0.0.124:5000//v3
export NOVA_VERSION=1.1
export OS_IMAGE_API_VERSION=2
export OS_PASSWORD=PASSWORD
export OS_PROJECT_DOMAIN_NAME=Default
export OS_IDENTITY_API_VERSION=3
export OS_PROJECT_NAME=admin
export OS_AUTH_TYPE=password
export PYTHONWARNINGS='ignore:Certificate has no, ignore:A true SSLContext object is not available'

# Add OS_CLOUDNAME to PS1
if [ -z "${CLOUDPROMPT_ENABLED:-}" ]; then
    export PS1=${PS1:-""}
    export PS1=\${OS_CLOUDNAME:+"(\$OS_CLOUDNAME)"}\ $PS1
    export CLOUDPROMPT_ENABLED=1
fi
(undercloud) [stack@undercloud-0 ~]$ source overcloudrc 
(overcloud) [stack@undercloud-0 ~]$ source stackrc 
(undercloud) [stack@undercloud-0 ~]$ printenv | grep no_proxy
no_proxy=,10.0.0.124,192.168.24.8
(undercloud) [stack@undercloud-0 ~]$ ./overcloud_deploy_nologs.sh
...
2020-04-01 04:00:52Z [overcloud]: UPDATE_COMPLETE  Stack UPDATE completed successfully

 Stack overcloud UPDATE_COMPLETE 

Started Mistral Workflow tripleo.deployment.v1.get_horizon_url. Execution ID: 259851c1-3675-4bf5-8aea-022646b0cce8
Overcloud Endpoint: http://10.0.0.124:5000/
Overcloud Horizon Dashboard URL: http://10.0.0.124:80/dashboard
Overcloud rc file: /home/stack/overcloudrc
Overcloud Deployed
(undercloud) [stack@undercloud-0 ~]$ cat overcloudrc 
# Clear any old environment that may conflict.
for key in $( set | awk '{FS="="}  /^OS_/ {print $1}' ); do unset $key ; done
export OS_NO_CACHE=True
export COMPUTE_API_VERSION=1.1
export OS_USERNAME=admin
export no_proxy=,10.0.0.124,192.168.24.8,10.0.0.124,192.168.24.8 <==========(*)
export OS_REGION_NAME=regionOne
export OS_USER_DOMAIN_NAME=Default
export OS_VOLUME_API_VERSION=3
export OS_CLOUDNAME=overcloud
export OS_AUTH_URL=http://10.0.0.124:5000//v3
export NOVA_VERSION=1.1
export OS_IMAGE_API_VERSION=2
export OS_PASSWORD=PASSWORD
export OS_PROJECT_DOMAIN_NAME=Default
export OS_IDENTITY_API_VERSION=3
export OS_PROJECT_NAME=admin
export OS_AUTH_TYPE=password
export PYTHONWARNINGS='ignore:Certificate has no, ignore:A true SSLContext object is not available'

# Add OS_CLOUDNAME to PS1
if [ -z "${CLOUDPROMPT_ENABLED:-}" ]; then
    export PS1=${PS1:-""}
    export PS1=\${OS_CLOUDNAME:+"(\$OS_CLOUDNAME)"}\ $PS1
    export CLOUDPROMPT_ENABLED=1
fi
(undercloud) [stack@undercloud-0 ~]$ 
~~~

Version-Release number of selected component (if applicable):

How reproducible:
Always

Steps to Reproduce:
1. deploy overcloud
2. Run '$ source ~/overcloudrc; source ~/stackrc'
3. rerun 'openstack overcloud deploy'

Actual results:
no_proxy in overcloud has duplicated items

Expected results:
no_proxy in overcloud doesn't have duplicated items

Additional info: