Convert fabric MTU to string for API call

Change-Id: I8cda30d1f26624533d6adda02158d605bf1e76e8
diff --git a/_modules/maasng.py b/_modules/maasng.py
index a96a4e4..c08d5db 100644
--- a/_modules/maasng.py
+++ b/_modules/maasng.py
@@ -1095,10 +1095,11 @@
     data = {
         "name": name,
         "dhcp_on": str(dhcp_on),
-        "mtu": mtu,
         "description": description,
         "primary_rack": list_racks()[primary_rack]['system_id'],
     }
+    if mtu:
+        data['mtu'] = str(mtu)
     vlan = str(vlan)
     maas = _create_maas_client()
     fabric_id = get_fabricid(fabric)
diff --git a/_states/maasng.py b/_states/maasng.py
index c574f22..b71c9d9 100644
--- a/_states/maasng.py
+++ b/_states/maasng.py
@@ -365,7 +365,7 @@
                                                            description=description,
                                                            primary_rack=primary_rack,
                                                            dhcp_on=dhcp_on)
-        ret['comment'] = 'Vlan {0} has' \
+        ret['comment'] = 'Vlan {0} has ' \
                          'been created for {1}'.format(name, fabric)
     elif _rez == 'update':
         _id = __salt__['maasng.list_vlans'](fabric)[vlan]['id']
@@ -378,7 +378,7 @@
                                                            dhcp_on=dhcp_on,
                                                            update=True,
                                                            vlan_id=_id)
-        ret['comment'] = 'Vlan {0} has been' \
+        ret['comment'] = 'Vlan {0} has been ' \
                          'updated for {1}'.format(name, fabric)
     ret['changes'] = changes
 
diff --git a/maas/region.sls b/maas/region.sls
index 04e2a1b..684fda4 100644
--- a/maas/region.sls
+++ b/maas/region.sls
@@ -314,7 +314,7 @@
 maas_vlan{{ vlan_n }}_present_for_{{ fabric_name }}:
   maasng.vlan_present_in_fabric:
   - vlan: {{ vlan_n }}
-  - mtu: {{ data.get('mtu','') }}
+  - mtu: {{ data.get('mtu', '') }}
   - fabric: {{ fabric_name }}
   - name: {{ data.get('name','') }}
   - description: {{ data.description }}
@@ -362,7 +362,7 @@
 maas_vlan{{ vlan_n }}_present_for_{{ fabric_name }}_dhcp:
   maasng.vlan_present_in_fabric:
   - vlan: {{ vlan_n }}
-  - mtu: {{ data.get('mtu','') }}
+  - mtu: {{ data.get('mtu', '') }}
   - fabric: {{ fabric_name }}
   - name: {{ data.get('name','') }}
   - description: {{ data.description }}