qemuFirmwareFetchConfigs: Fix check for @privileged

qemuFirmwareFetchConfigs: Fix check for @privileged

The qemuFirmwareFetchConfigs() function is supposed to fetch all
firmware descriptions from paths defined by firmware.json
specification. This includes user's $HOME directory. However, it
was agreed that if libvirtd is running as privileged user then
his $HOME is ignored (thus $HOME is included in the search only
for regular users). Well, I got the condition wrong - it should
have been reversed.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>