it couldn't parse the --ssl option.

client/mysql_upgrade.c:
  mysql_upgrade parses its options and passes some of them to the underlying
  tools (mysqlcheck etc). To do this passdown, it reconstructs a
  command-line-suitable text from the my_option object (which
  contains the option's name and option's value). For options
  which expect no parameter, it just had to use the option's name;
  for other options, it had to concatenate the option's name,
  a "=" symbol, and the option's value; it had code to handle
  this latter case, but only for GET_STR options (options taking a
  string as value). But since the work on WL 4738, the --ssl
  option, a GET_BOOL, which used to have no parameter (NO_ARG), can
  now have one (OPT_ARG), so with --ssl we came to the "default"
  label, error. Fixed by constructing the command-line-suitable
  representation for GET_BOOL too. For --ssl it will produce
  --ssl=1 ; for --ssl=0, it will produce --ssl=0.
mysql-test/include/mysql_upgrade_preparation.inc:
  handles requirements of tests which use mysql_upgrade
mysql-test/r/mysql_upgrade_ssl.result:
  result; without the code fix we would get "internal error".
mysql-test/t/mysql_upgrade.test:
  This test has requirements before running; moved them
  to an include file in order to share with mysql_upgrade_ssl.
mysql-test/t/mysql_upgrade_ssl.test:
  test for bug. Couldn't go into mysql_upgrade.test as this new test requires
  SSL support. --force is needed, in case mysql_upgrade.test run before
  (in which case mysql_upgrade_ssl would say that upgrade has already been
  done); --force forces the upgrade in all cases.