Clear the caches *after* loading authzones.

[omoerbeek]

Short description

Fix a race between (re)loading an authzone and wiping the caches.

Checklist

I have:

• [X] read the CONTRIBUTING.md document
• [X] compiled this code
• [X] tested this code
• [ ] included documentation (including possible behaviour changes)
• [X] documented the code
• [ ] added or modified regression test(s)
• [ ] added or modified unit test(s)

[paddg]

Your solution works for us, the problem has gone. Thanks!! We would be grateful if you could backport this to 4.7.x if possible.

[omoerbeek]

Thanks for testing! This will be backported to 4.7.x.