Accounts with expired passwords will prevent most statements
from being executed until a new password is set. A side effect
is that a user who needs to change the PASSWORD() algorithm will
be blocked from changing the old_passwords variable and
consequently won't be able to reset his password.

Some connectors also issue SET statements to initialize a new
connection and they will also fail if these statements are
blocked.

This patch fixes both issues by allowing for all kinds of
SET statements even a password is expired.