Action "synchronize" ignores no_proxy env vars when calling sstream-mirror

[Przemyslaw Lal]

In _on_synchronize_action method in charm.py lines 77-80 the code propagates http and https proxy env variables, but ignores no_proxy. This results in sstream-mirror always hitting proxy server which breaks the "synchronize" action when image-source is included in no_proxy value.

Possible workaround is to comment out lines 77-80 so that ignores proxy settings completely, but the proper long-term solution would be to correctly propagate no_proxy variable.

[Robert Gildein (rgildein)]

PR: https://github.com/canonical/charm-simple-streams/pull/8