Fix variable name
Fix variable name

TrivialFix

The customization format of the variable name should contain the
<image_name> [1]. This change fixes the name of the 'remote_apt_keys'
variable in base Dockerfile.

1. https://docs.openstack.org/kolla/latest/admin/image-building.html#dockerfile-customisation

Change-Id: I423db39e77f337a73d3d88e3dbd56469be45110b
Signed-off-by: Maksim Malchuk <628dbb6f3e6f66faed1622da41383b30036b33e1@gmail.com>

openstack/kolla,openstack/kolla