During shutdown period of vmalert, remotewrite client retrieve all pending time series from buffer queue, compose them into 1 batch and execute remote write.
This final batch may exceed the limit of -remoteWrite.maxBatchSize, and be rejected by the receiver (gateway, vmcluster or others).
This changes ensures that even during shutdown vmalert won't exceed the max batch size limit for remote write
destination.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6025
(cherry picked from commit 623d257faf)
Signed-off-by: hagen1778 <roman@victoriametrics.com>