Fix hostcfgd, so mgmt interface can be deleted when no gw was given during add

Author: ashutosh-cs

scripts/hostcfgd

@@ -1585,21 +1585,42 @@ class MgmtIfaceCfg(object):
     def update_mgmt_iface(self, iface, key, data):
         """Handle update management interface config
         """
-        syslog.syslog(syslog.LOG_DEBUG, 'MgmtIfaceCfg: mgmt iface update')
+        syslog.syslog(syslog.LOG_DEBUG, 'TEST-1 MgmtIfaceCfg: Starting interface update')
 
-        # Restart management interface service when config was changed
-        if data != self.iface_config_data.get(key):
-            cfg = {key: data}
-            syslog.syslog(syslog.LOG_INFO, f'MgmtIfaceCfg: Set new interface '
-                                           f'config {cfg} for {iface}')
-            try:
-                run_cmd(['sudo', 'systemctl', 'restart', 'interfaces-config'], True, True)
-            except subprocess.CalledProcessError:
-                syslog.syslog(syslog.LOG_ERR, f'Failed to restart management '
-                              'interface services')
-                return
+        existing_data = self.iface_config_data.get(key)
 
+        # Check if data has changed
+        if data != existing_data:
+            syslog.syslog(syslog.LOG_INFO, f'TEST-2 MgmtIfaceCfg: Updating config for {iface} with {data}')
+            # Update the interface configuration
             self.iface_config_data[key] = data
+        elif not data:
+            # If new data is empty, remove the key if it exists
+            if key in self.iface_config_data:
+                self.iface_config_data.pop(key)
+                syslog.syslog(syslog.LOG_INFO, f'TEST-3 MgmtIfaceCfg: Removed config for {iface}')
+                
+                # This entry is created explicitly by sonic-gnmi, but during delete, this entry is not deleted.
+                # This causes the interface.j2 to think static ip is still configured
+                subprocess.run(['redis-cli', '-n', '4', 'DEL', f'MGMT_INTERFACE|{iface}', '', ''], check=True)
+            else:
+                syslog.syslog(syslog.LOG_DEBUG, f'TEST-4 MgmtIfaceCfg: No existing config to remove for {iface}')
+                # No change; no need to restart services
+                return
+        else:
+            # Data hasn't changed; no need to proceed
+            syslog.syslog(syslog.LOG_DEBUG, f'TEST-5 MgmtIfaceCfg: No changes detected for {iface}')
+            return
+
+        # Restart services after configuration change
+        try:
+            syslog.syslog(syslog.LOG_INFO, f'TEST-6 MgmtIfaceCfg: Updated:{self.iface_config_data}')
+
+            run_cmd(['sudo', 'systemctl', 'restart', 'interfaces-config'], True, True)
+
+            syslog.syslog(syslog.LOG_INFO, 'TEST-7 MgmtIfaceCfg: Successfully restarted services')
+        except subprocess.CalledProcessError:
+            syslog.syslog(syslog.LOG_ERR, 'TEST-8 MgmtIfaceCfg: Failed to restart management interface services')
 
     def update_mgmt_vrf(self, data):
         """Handle update management VRF state