cfg: Get rid of all .sample sufixes

This is frequently a source of confusion among users,
so let's drop the .sample prefixes and use only .cfg
for all the config files. We can always exclude the
copied/auto generated ones using .gitignore.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

.gitignore

@@ -18,3 +18,16 @@
 shared/data
 kvm/env
 logs
+kvm/cfg/base.cfg
+kvm/cfg/cdkeys.cfg
+kvm/cfg/guest-hw.cfg
+kvm/cfg/guest-os.cfg
+kvm/cfg/subtests.cfg
+kvm/cfg/virtio-win.cfg
+libvirt/cfg/base.cfg
+libvirt/cfg/cdkeys.cfg
+libvirt/cfg/guest-hw.cfg
+libvirt/cfg/guest-os.cfg
+libvirt/cfg/subtests.cfg
+libvirt/cfg/virtio-win.cfg
+tmp