Fix Moodle 4.5 delete global blog issue

[owenherbert-catalyst]

This patch updates the function to return true instead of false when skipping deletion of a global blog. This ensures the ad-hoc task completes gracefully in Moodle 4.5. After the change we get Adhoc task complete instead of Adhoc task failed.

Before plugin code change:

Execute adhoc task: core_course\task\course_delete_modules
Adhoc task id: 3018
Adhoc task custom data: {"cms":[{"id":"1","course":"1","module":"55","instance":"1","section":"2","idnumber":null,"added":"1549578973","score":"0","indent":"0","visible":"0","visibleoncoursepage":"1","visibleold":"0","groupmode":"0","groupingid":"0","completion":"0","completiongradeitemnumber":null,"completionview":"0","completionexpected":"0","showdescription":"0","availability":null,"deletioninprogress":"1","completionpassgrade":"0","downloadcontent":"1","lang":null}],"userid":"174","realuserid":"174"}
... started 09:51:56. Current memory use 22.3 MB.
++ Skipping deletion of global blog (ID: 1). Global blogs cannot be deleted. ++
* line 135 of /mod/oublog/lib.php: call to debugging()
* line 753 of /course/lib.php: call to oublog_delete_instance()
* line 68 of /course/classes/task/course_delete_modules.php: call to course_delete_module()
* line 517 of /lib/classes/cron.php: call to core_course\task\course_delete_modules->execute()
* line 348 of /lib/classes/cron.php: call to core\cron::run_inner_adhoc_task()
* line 148 of /admin/cli/adhoc_task.php: call to core\cron::run_adhoc_task()
... used 11 dbqueries
... used 0.24819278717041 seconds
Adhoc task failed: core_course\task\course_delete_modules,Coding error detected, it must be fixed by a programmer: The following course modules could not be deleted:
 The course module 1 could not be deleted. error/cannotdeletemoduleinstance (Cannot delete the module oublog (instance).): /var/www/miclearn/course/lib.php(754) #0 /var/www/miclearn/course/classes/task/course_delete_modules.php(68): course_delete_module('1')
#1 /var/www/miclearn/lib/classes/cron.php(517): core_course\task\course_delete_modules->execute()
#2 /var/www/miclearn/lib/classes/cron.php(348): core\cron::run_inner_adhoc_task(Object(core_course\task\course_delete_modules))
#3 /var/www/miclearn/admin/cli/adhoc_task.php(148): core\cron::run_adhoc_task(3018)
#4 {main}
Backtrace:
* line 517 of /lib/classes/cron.php: call to core_course\task\course_delete_modules->execute()
* line 348 of /lib/classes/cron.php: call to core\cron::run_inner_adhoc_task()
* line 148 of /admin/cli/adhoc_task.php: call to core\cron::run_adhoc_task()

After plugin code change:

Execute adhoc task: core_course\task\course_delete_modules
Adhoc task id: 3018
Adhoc task custom data: {"cms":[{"id":"1","course":"1","module":"55","instance":"1","section":"2","idnumber":null,"added":"1549578973","score":"0","indent":"0","visible":"0","visibleoncoursepage":"1","visibleold":"0","groupmode":"0","groupingid":"0","completion":"0","completiongradeitemnumber":null,"completionview":"0","completionexpected":"0","showdescription":"0","availability":null,"deletioninprogress":"1","completionpassgrade":"0","downloadcontent":"1","lang":null}],"userid":"174","realuserid":"174"}
... started 09:29:44. Current memory use 22.3 MB.
++ Skipping deletion of global blog (ID: 1). Global blogs cannot be deleted. ++
* line 135 of /mod/oublog/lib.php: call to debugging()
* line 753 of /course/lib.php: call to oublog_delete_instance()
* line 68 of /course/classes/task/course_delete_modules.php: call to course_delete_module()
* line 517 of /lib/classes/cron.php: call to core_course\task\course_delete_modules->execute()
* line 348 of /lib/classes/cron.php: call to core\cron::run_inner_adhoc_task()
* line 148 of /admin/cli/adhoc_task.php: call to core\cron::run_adhoc_task()
... used 110 dbqueries
... used 0.20869612693787 seconds
Adhoc task complete: core_course\task\course_delete_modules
++ No configured queue ++
* line 136 of /admin/tool/log/store/standardqueued/classes/log/store.php: call to debugging()
* line 106 of /admin/tool/log/classes/helper/buffered_writer.php: call to logstore_standardqueued\log\store->insert_event_entries()
* line 132 of /admin/tool/log/classes/helper/buffered_writer.php: call to logstore_standard\log\store->flush()
* line 195 of /admin/tool/log/classes/log/manager.php: call to logstore_standard\log\store->dispose()
* line 167 of /lib/classes/shutdown_manager.php: call to tool_log\log\manager->dispose()
* line ? of unknownfile: call to core_shutdown_manager::shutdown_handler()