dom0/core: setup yum to use proxy when it have access to it (#568)

To simplify configuration, automatically enable 'yum-proxy-setup'
pseudo-service when allowing access to the proxy. Also disable this service,
when access is revoked. Thanks to this the user can enable this feature by one
click in firewall settings.

dom0/qvm-core/qubes.py

@@ -1211,6 +1211,13 @@ class QubesVm(object):
                     os.path.basename(sys.argv[0]), err)
             return False
 
+        # Automatically enable/disable 'yum-proxy-setup' service based on allowYumProxy
+        if conf['allowYumProxy']:
+            self.services['yum-proxy-setup'] = True
+        else:
+            if self.services.has_key('yum-proxy-setup'):
+                self.services.pop('yum-proxy-setup')
+
         return True
 
     def has_firewall(self):

dom0/qvm-tools/qvm-firewall

@@ -314,6 +314,7 @@ def main():
         if vm.is_running():
             if vm.netvm is not None and vm.netvm.is_proxyvm():
                 vm.netvm.write_iptables_xenstore_entry()
+        qvm_collection.save()
 
     if not options.do_list:
         qvm_collection.unlock_db()