Lock content adapted to the ref implementation

See https://github.com/cs3org/cs3apis/blob/main/cs3/storage/provider/v1beta1/resources.proto
And cs3org/cs3apis#160

src/core/commoniface.py

@@ -27,8 +27,11 @@
 def genrevalock(appname, value):
     '''Return a base64-encoded lock compatible with the Reva implementation of the CS3 Lock API'''
     return urlsafe_b64encode(json.dumps(
-        {'h': appname if appname else 'wopi', 't': int(time.time()), 'md': value}
-        ).encode()).decode()
+        {'type': 'LOCK_TYPE_SHARED',
+         'h': appname if appname else 'wopi',
+         'md': value,
+         'mtime': int(time.time()),
+        }).encode()).decode()
 
 def retrieverevalock(rawlock):
     '''Restores the JSON payload from a base64-encoded Reva lock'''