Azure pipeline: report failure in prepare-build step
The azure pipeline defines a "prepare build" step that
installs the FreeIPA development dependencies but the
step does not report failures of the dnf builddep command.
As a consequence, subsequent steps may fail (for instance
because of components not installed such as tox) but are
hard to diagnose.
The fix reports the command failure.
Fixes: https://pagure.io/freeipa/issue/8022
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>