Call hooks for installation clients

The UI widget will be shown only when there are some failed hooks, that means:
* customer must have put some hook files there
* they must have failed

Following hooks are available:
* installation_start  
[... here will be called the hooks from ```ProductControl``` module ... ]
* before_finish
* before_copy_files_finish
* after_copy_files_finish
* before_copy_systemfiles_finish
* after_copy_systemfiles_finish
* before_switch_scr_finish
* after_switch_scr_finish
* before_ldconfig_finish
* after_ldconfig_finish
* before_save_config_finish
* after_save_config_finish
* before_default_target_finish
* after_default_target_finish
* before_desktop_finish
* after_desktop_finish
* before_storage_finish
* after_storage_finish
* before_iscsi-client_finish
* after_iscsi-client_finish
* before_kernel_finish
* after_kernel_finish
* before_x11_finish
* after_x11_finish
* before_proxy_finish
* after_proxy_finish
* before_pkg_finish
* after_pkg_finish
* before_driver_update1_finish
* after_driver_update1_finish
* before_random_finish
* after_random_finish
* before_system_settings_finish
* after_system_settings_finish
* before_bootloader_finish
* after_bootloader_finish
* before_kdump_finish
* after_kdump_finish
* before_yast_inf_finish
* after_yast_inf_finish
* before_network_finish
* after_network_finish
* before_firewall_stage1_finish
* after_firewall_stage1_finish
* before_ntp-client_finish
* after_ntp-client_finish
* before_save_hw_status_finish
* after_save_hw_status_finish
* before_users_finish
* after_users_finish
* before_installation_settings_finish
* after_installation_settings_finish
* before_driver_update2_finish
* after_driver_update2_finish
* before_pre_umount_finish
* after_pre_umount_finish
* before_copy_logs_finish
* after_copy_logs_finish
* before_umount_finish
* after_umount_finish
and
* installation_finish