testing: f25 add kernel-devel package from fedora repository

pull it from fedora repository by disabling "updates" repository.
then disable dnf kernel updates. Control the kernel update.

dnf repolist
Last metadata expiration check: 0:36:02 ago on Tue Jun 13 08:44:15 2017.
repo id 	repo name                       status
*fedora 	Fedora 25 - x86_64   		51,669
*updates        Fedora 25 - x86_64 - Updates    19,965

testing/libvirt/fedora25.ks

@@ -88,8 +88,10 @@ rpm -qa > /var/tmp/rpm-qa-fedora.log
 
 rpm -e vim-minimal --nodeps
 
-# echo "exclude=kernel*" >> /etc/dnf/dnf.conf
-# dnf -y update 2>&1 | tee /var/tmp/dnf-update.log
+dnf -y --disablerepo=updates update | tee /var/tmp/dnf-update-fedora.log
+dnf -y --disablerepo=updates install kernel-devel
+sed -i '/exclude=kernel/d' /etc/dnf/dnf.conf
+echo "exclude=kernel*" >> /etc/dnf/dnf.conf
 
 mkdir /testing /source