cls/rbd: drop overzealous CLS_ERR message in mirror_remote_namespace_get()

Currently it unnecessarily floods the log of the OSD which hosts
rbd_mirroring object with "No such file or directory" errors.  Just
drop it as read_key() already logs all errors except ENOENT.

Credit to N Balachandran <[email protected]> for spotting this.

Signed-off-by: Ilya Dryomov <[email protected]>

Author: idryomov

src/cls/rbd/cls_rbd.cc

@@ -5938,8 +5938,6 @@ int mirror_remote_namespace_get(cls_method_context_t hctx, bufferlist *in,
   std::string mirror_ns_decode;
   int r = read_key(hctx, mirror::REMOTE_NAMESPACE, &mirror_ns_decode);
   if (r < 0) {
-    CLS_ERR("error getting mirror remote namespace: %s",
-            cpp_strerror(r).c_str());
     return r;
   }