Do not disable caching for apt when http proxies are configured

This patch removes code which detected http proxies being set in
environment variables, and inserted an apt configuration instructing
those proxies not to perform caching.

This lack of caching reduces the effectiveness of an http proxy which
has caching enabled - a common technique for increasing performance of
operating system installs without having to run a full mirror of
upstream repositories.

If a deployer is faced with a proxy server which in some way breaks
upstream package repository interactions, this no-cache setting can be
applied by the deployer as part of host preparation and will be
duplicated into containers by the OSA tooling.

Change-Id: I62293c723353ffb986db1cddc5d0da20ae0df447

releasenotes/notes/remove-proxy-no-cache-9b514030c87e7d1b.yaml

@@ -0,0 +1,14 @@
+---
+other:
+  - |
+    Code which added 'Acquire::http:No-Cache true' to the host and container
+    apt preferences when http proxy environment variables were set has been
+    removed. This setting is only required when working around issues
+    introduced by badly configured http proxies. In some cases proxies can
+    improperly cache the apt Releases and Packages files leading to package
+    installation errors. If a deployment is behind a badly configured proxy,
+    the deployer can add the necessary apt config fragment as part of host
+    provisioning. OSA will replicate that config into any containers that
+    are created. This setting can be removed from existing deployments if
+    required by manually deleting the file
+    ``/etc/apt/apt.conf.d/00apt-no-cache`` from all host and containers.

tasks/configure_metal_hosts.yml

@@ -22,21 +22,6 @@
   when:
     - ansible_kernel | version_compare(openstack_host_required_kernel, '<')
 
-- name: Disable cache for apt update for hosts
-  copy:
-    content: |
-      Acquire::http::No-Cache true;
-    dest: "/etc/apt/apt.conf.d/00apt-no-cache"
-  tags:
-    openstack_hosts-config
-  when:
-    - ansible_pkg_mgr == 'apt'
-    - >
-      global_environment_variables.http_proxy is defined or
-      global_environment_variables.HTTP_PROXY is defined or
-      global_environment_variables.https_proxy is defined or
-      global_environment_variables.HTTPS_PROXY is defined
-
 - name: Install distro packages for bare metal nodes
   package:
     name: "{{ openstack_host_metal_distro_packages }}"