rgw: dont log EBUSY errors in 'sync error list'

these temporary errors get retried automatically, so no admin
intervention is required. logging them only serves to waste space in
omap and obscure the more serious sync errors

Fixes: http://tracker.ceph.com/issues/22473

Signed-off-by: Casey Bodley <cbodley@redhat.com>

src/rgw/rgw_data_sync.cc

@@ -1037,10 +1037,13 @@ class RGWDataSyncSingleEntryCR : public RGWCoroutine {
       }
 
       if (sync_status < 0) {
-        yield call(sync_env->error_logger->log_error_cr(sync_env->conn->get_remote_id(), "data", raw_key,
-                                                        -sync_status, string("failed to sync bucket instance: ") + cpp_strerror(-sync_status)));
-        if (retcode < 0) {
-          tn->log(0, SSTR("ERROR: failed to log sync failure: retcode=" << retcode));
+        // write actual sync failures for 'radosgw-admin sync error list'
+        if (sync_status != -EBUSY && sync_status != -EAGAIN) {
+          yield call(sync_env->error_logger->log_error_cr(sync_env->conn->get_remote_id(), "data", raw_key,
+                                                          -sync_status, string("failed to sync bucket instance: ") + cpp_strerror(-sync_status)));
+          if (retcode < 0) {
+            tn->log(0, SSTR("ERROR: failed to log sync failure: retcode=" << retcode));
+          }
         }
         if (error_repo && !error_repo->append(raw_key)) {
           tn->log(0, SSTR("ERROR: failed to log sync failure in error repo: retcode=" << retcode));