newvm: Add host to some groups by default

There are some groups that all hosts should belong to in almost all
cases.  Rather than have to remember to add the `--group` arguments for
each of these, the `newvm.sh` script will now enable them by default.
For hosts that should _not_ belong to (at least one of) these groups,
the `--no-default-groups` argument can be provided to suppress that
behavior.

The default groups, initially, are _chrony_ and _collectd_.

newvm.sh

@@ -8,9 +8,10 @@ vcpus=2
 disk_size=16
 kickstart=https://git.pyrocufflink.net/infra/kickstart/raw/branch/master/fedora.ks
 fedora=$(rpm -E %fedora)
-network=network=prod
-dnsdomain=pyrocufflink.blue
+network=network=kube
+dnsdomain=host.pyrocufflink.black
 console=true
+default_groups=true
 
 usage() {
     printf 'usage: %s [options] name\n' "${0##*/}"
@@ -89,6 +90,9 @@ while [ $# -gt 0 ]; do
     --group=*)
         groups_xml="${groups_xml}<group name=\"${1#*=}\"/>"
         ;;
+    --no-default-groups)
+        default_groups=false;
+        ;;
     --no-console|--noconsole)
         console=false
         ;;
@@ -129,6 +133,11 @@ if [ -z "${LIBVIRT_DEFAULT_URI}" ]; then
     exit 1
 fi
 
+if ${default_groups}; then
+    groups_xml="<group name=\"chrony\"/>${groups_xml}"
+    groups_xml="<group name=\"collectd\"/>${groups_xml}"
+fi
+
 printf 'Creating %s on %s\n' "${name}" "${LIBVIRT_DEFAULT_URI}"
 
 if [ -z "${location}" ]; then