unbound testsuite fails on mock build in systemd-nspawn if systemd support is build

[bleve]

test suite fails in mock when using systemd-snawn continaier for build when unbound is build with --enable-systemd. testsuite works fine if unbound is build without systemd support.

I guess test suite should disable use of notify.

Version 1.12.0.

[wcawijngaards]

The fix should remove the issue, it unsets the environment variable that systemd uses to enable the notification. I guess this variable is somehow set for the entire container, instead of just for the server startup.