Online schema migration causes the master to report a very high or negative number of QPS

We've seen this a few times when making an online schema change, e.g.:

alter 'foo', {NAME=>'e',VERSIONS=>'2147483646'} 

This causes the master to briefly show extremely high QPS per regionserver, and probably causes an integer overflow in the sum.

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This could be related to the issue reported in HBASE-27242.