fix reading of ednsflags in recursor testing

[Habbie]

Short description

We parsed the DNS header flags section as if it were the EDNS flags section. Due to the placement of the QR and DO bit in these sections respectively, this caused all testcases to always see a DO bit.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled and tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master

[Habbie]

This will be red on Travis until #5618 is fixed.

[pieterlexis]

Pleas rebase on master, the underlying issue is fixed.

[Habbie]

Rebased but not tested

[Habbie]

Force-pushed a fix for something I was confused about cosmetically in our tests. Thanks @pieterlexis. This should pass now.