Bug #44797 plugins w/o command-line options have no disabling option in --help

Description:
For every plugin there are two command-line options created automatically:

  --XXX
  --plugin-XXX

(if the plugin name is XXX). For example --innodb and --plugin-innodb.

But mysqld --help does not print them for plugins that don't have other command-line options.

How to repeat:
run mysqld --skip-archive.
check with 'show plugins' that it worked.
run mysqld --help, note that there's no --archive option there.

Suggested fix:
in my_print_help_inc_plugins() remove p->plugin->system_vars from the if()

Pushed into 5.5.3-m3 (revid:alik@sun.com-20100306103849-hha31z2enhh7jwt3) (version source revid:vvaintroub@fedora12-20091225154921-x25a5pyw1pxiwobv) (merge vers: 5.5.99) (pib:16)

Noted in 5.5.3 changelog.

For plugins that did not have command-line options other than the
ones to select the plugin itself, those options were not displayed in
the mysqld help message.