ui_tests: extend test_config.py suite
    
    Extend test_config.py suite with new test cases.
    
    Added tests:
    
    config_email_undo
    config_groupsearch_reset
    groupsearchfield_blank
    groupsearchfield_existing
    groupsearchfield_leading_space
    groupsearchfield_notallowed
    groupsearchfield_trailing_space
    usersearchfield_trailing_space
    sizelimit_blank
    sizelimit_letter
    sizelimit_space
    timelimit_blank
    timelimit_letter
    timelimit_negative
    timelimit_space
    userDefaultShell_blank
    userDefaultShell_leading_space
    userDefaultShell_new
    userDefaultShell_specialchar
    userDefaultShell_trailing_space
    useremail_leading_space
    useremail_new
    useremail_trailing_space
    usergroup_new
    userhomedir_blank
    userhomedir_leading_space
    userhomedir_numbers
    userhomedir_space_inbetween
    userhomedir_specialchar
    userhomedir_trailing_space
    usermigrationmode_disable
    usermigrationmode_enable
    usernamelength_blank
    usernamelength_letters
    usernamelength_max
    usernamelength_new
    usernamelength_space_inbetween
    usernamelength_specialchar
    userpwdexpnotify_blank
    userpwdexpnotify_letters
    userpwdexpnotify_max
    userpwdexpnotify_space_inbetween
    userpwdexpnotify_specialchar
    usersearchfield_blank
    usersearchfield_existing
    usersearchfield_leading_space
    usersearchfield_new
    usersearchfield_notallowed
    
    https://pagure.io/freeipa/issue/7576
    
    Reviewed-By: Pavel Picka <ppicka@redhat.com>