[This patch has already been approved by Serge.  I am recommitting and pushing from a new repository because there were other changesets that couldn't be pushed.]

BUG# 5229 --password=foobar does not override the empty 'password' option in the my.cnf
This is a backport of a change made by jani in the 4.1 tree.

mysql.cc:
  Add tty_password=0 in the p case handling in get_one_option