Test chart upgrade

[andresmgot]

Description of the change

The goal of this PR is to add a basic test to ensure we don't break the upgrade process (at least with the flags we use in our CI system). To avoid having another build or run the upgrade test for every build I am adding the env var TEST_UPGRADE to the PostgreSQL + Helm 3 scenario (the "recommended" setup).

The test is just installing the kubeapps chart from the bitnami repository and upgrading it afterwards with the status of the current chart folder.

Benefits

Breaking changes in the chart will be noticed.

Applicable issues

• fixes CI should test chart upgrades #1544

[absoludity]

Nice solution Andres. +1 for only testing with the recommended setup for now - we can't test all combinations (and the sooner we get the combinations down, the better), but one thing this won't allow is testing a mongodb install upgrading to pg, for example?

[andresmgot]

Nice solution Andres. +1 for only testing with the recommended setup for now - we can't test all combinations (and the sooner we get the combinations down, the better), but one thing this won't allow is testing a mongodb install upgrading to pg, for example?

yes, we are not covering that use case (which is a corner case anyway). When doing "weird" changes to the default values we need to handle them carefully anyway.