Decrement commitBatchesMemBytesCount when rejecting commit batch

[sfc-gh-nwijetunga]

This issue relates to: #4523

We were never decrementing commitBatchesMemBytesCount when rejecting a commit batch causing this value to "blow up". This PR address this to make sure we are decrementing before returning.

This PR passes 10k Joshua runs

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[jzhou77]

Thank you for finding and fixing this bug!