mech: Compress empty yang containers in CLI

E.g. instead of: `set interfaces interface eth0`

We can now say: `set interface eth0`

src/mech/clixon.xml.in

@@ -27,6 +27,14 @@
   <CLICON_STREAM_DISCOVERY_RFC5277>true</CLICON_STREAM_DISCOVERY_RFC5277>
   <CLICON_YANG_LIBRARY>false</CLICON_YANG_LIBRARY>
   <CLICON_BACKEND_RESTCONF_PROCESS>true</CLICON_BACKEND_RESTCONF_PROCESS>
+  <autocli>
+    <rule>
+      <name>compress</name>
+      <operation>compress</operation>
+      <yang-keyword>container</yang-keyword>
+      <yang-keyword-child>list</yang-keyword-child>
+    </rule>
+  </autocli>
   <restconf>
     <enable>true</enable>
     <fcgi-socket>@RUNSTATEDIR@/clixon/restconf.sock</fcgi-socket>