The problem is that the internal variable used to specify a
transaction with consistent read was being used outside the
processing context of a START TRANSACTION WITH CONSISTENT
SNAPSHOT statement. The practical consequence was that a
consistent snapshot specification could leak to unrelated
transactions on the same session.

The solution is to ensure a consistent snapshot clause is
only relied upon for the START TRANSACTION statement.

This is already fixed in a similar way on 6.0.

mysql-test/r/consistent_snapshot.result:
  Add test case result for Bug#44664
mysql-test/t/consistent_snapshot.test:
  Add test case for Bug#44664
sql/sql_parse.cc:
  The WITH CONSISTENT SNAPSHOT clause is only valid for the
  START TRANSACTION statement.