Fix default available IPs

We should reserve 10 addresses at the beginning and 5 at the end.
Meaning for a /24 network, we should start at 11 and end at 249.

app/network/views.py

@@ -415,9 +415,9 @@ def retrieve_ips(subnet, prefix):
         data = {'ips': [], 'first': '', 'last': ''}
     else:
         hosts = [str(ip) for ip in address.hosts()]
-        if len(hosts) > 15:
-            first = hosts[9]
-            last = hosts[-5]
+        if len(hosts) > 17:
+            first = hosts[10]
+            last = hosts[-6]
         else:
             first = hosts[0]
             last = hosts[-1]