Fix: keep hestia-users group id outside normal user id range

bin/v-add-user

@@ -63,7 +63,7 @@ echo "$user:$password" | /usr/sbin/chpasswd
 
 # Add a general group for normal users created by Hestia
 if [ -z "$(grep ^hestia-users: /etc/group)" ]; then
-    groupadd "hestia-users"
+    groupadd --system "hestia-users"
 fi
 
 # Add membership to hestia-users group to non-admin users

install/upgrade/0.10.0-190430.sh

@@ -182,7 +182,7 @@ fi
 
 # Add a general group for normal users created by Hestia
 if [ -z "$(grep ^hestia-users: /etc/group)" ]; then
-    groupadd "hestia-users"
+    groupadd --system "hestia-users"
 fi
 
 # Make sure non-admin users belong to correct Hestia group