network: Fixes salt-lint errors 207, 208

network/ifupdown2.sls

@@ -17,7 +17,7 @@ clean /etc/systemd/network/:
     - name: /etc/systemd/network
     - user: root
     - group: root
-    - mode: 755
+    - mode: '0755'
     - clean: true
 
 # Reload interface configuration if neccessary

network/systemd.sls

@@ -19,7 +19,7 @@ clean /etc/network/interfaces.d/:
     - name: /etc/network/interfaces.d
     - user: root
     - group: root
-    - mode: 755
+    - mode: '0755'
     - clean: true
 
 systemd-networkd.service: