Read secret file before each authentication attempt

[bbetter173]

This PR removes the secret variable from the controller and instead reads the secret file before each authentication attempt.

Fixes #56 by ensuring that the correct password is used for all reloads.

Relevant varnish docs: https://github.com/varnishcache/varnish-cache/blob/606977bbfb624ead38e9c8648beac0b3906a4294/doc/sphinx/users-guide/run_security.rst#cli-interface-authentication, specifically:

You can change the contents of the secret file while varnishd runs, it is read every time a CLI connection is authenticated.

[mittwald-machine]

There has not been any activity to this pull request in the last 14 days. It will automatically be closed after 7 more days. Remove the stale label to prevent this.

[bbetter173]

@martin-helmich - Sorry to ping, but any chance this could be reviewed before it's closed off as stale? Thanks!

[mittwald-machine]

There has not been any activity to this pull request in the last 14 days. It will automatically be closed after 7 more days. Remove the stale label to prevent this.

[bbetter173]

@martin-helmich Can we please remove the stale tag?

[martin-helmich]

Apologies. This should not have gotten stale.

[martin-helmich]

👍 LGTM -- thanks for your contribution.

[robmoore]

I believe we have been seeing this issue in our environment. It doesn't appear that this change made it to 0.7.0. Is it possible it may be included in a release soon?