Import qubes RPM keys (#780)

So the user would not get surprised by key confirmation dialog on the
first update.

scripts_fedora/04_install_qubes.sh

@@ -6,6 +6,8 @@ echo "--> Installing RPMs..."
 export YUM0=$PWD/yum_repo_qubes
 yum install -c $PWD/yum.conf $YUM_OPTS -y --installroot=$(pwd)/mnt @qubes-vm || RETCODE=1
 
+rpm --root=$PWD/mnt --import $PWD/mnt/etc/pki/rpm-gpg/RPM-GPG-KEY-qubes-*
+
 echo "--> Installing 3rd party apps"
 $SCRIPTSDIR/add_3rd_party_software.sh || RETCODE=1