All statements executed by mysql_upgrade are binlogged and then are replicated to slave.
This will result in some errors. The report of this bug has demonstrated some examples.

Master and slave should be upgraded separately. All statements executed by
mysql_upgrade will not be binlogged. 
--write-binlog and --skip-write-binlog options are added into mysql_upgrade. 
These options control whether sql statements are binlogged or not.