Fail test when libvirtd fails to reload on time

[ldoktor]

More and more often I'm getting weird failures on a very overloaded machine when the libvirtd fails to reload on time and they all look related to us using libvirt before it's started. Let's fail the test in such case during the setup instead of silently proceeding.

[ldoktor]

Changes:

• fixed the check for None (both None and False should fail)

Not changed:

• the timeout as param/variable. I am open to turning it into a class variable if you insisted, but please re-consider the real user action in case they want to tweak it https://github.com/avocado-framework/avocado-vt/pull/2453/commits/4514fad0dba16841f019cc0ae7c0f2a1802b1ffc#r399023337