test/json: Fix: Add missing function declaration

to clear nvmf subsystem.

Change-Id: I0bc33a3edf62b8248b9b6b33fa33be59ea400868
Signed-off-by: Pawel Kaminski <pawelx.kaminski@intel.com>
Reviewed-on: https://review.gerrithub.io/412941
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Paweł Niedźwiecki <pawelx.niedzwiecki@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

test/json_config/clear_config.py

@@ -85,6 +85,10 @@ def clear_bdev_subsystem(args, bdev_config):
             args.client.call(destroy_method, {bdev_name_key: bdev_name})
 
 
+def clear_nvmf_subsystem(args, nvmf_config):
+    pass
+
+
 def clear_scsi_subsystem(args, scsi_config):
     pass