fix: Call execute until it is removed for Job class

Because if an application extends execute it will change behavior
 without warning otherwise.

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

core/Command/Background/Job.php

 			$output->writeln('<error>Something went wrong when trying to retrieve Job with ID ' . $jobId . ' from database</error>');
 			return 1;
 		}
-		$job->start($this->jobList);
+		/** Calling execute until it is removed, then will switch to start */
+		$job->execute($this->jobList);
 		$job = $this->jobList->getById($jobId);
 
 		if (($job === null) || ($lastRun !== $job->getLastRun())) {

cron.php

 			$memoryBefore = memory_get_usage();
 			$memoryPeakBefore = memory_get_peak_usage();
 
-			$job->start($jobList);
+			/** Calling execute until it is removed, then will switch to start */
+			$job->execute($jobList);
 
 			$memoryAfter = memory_get_usage();
 			$memoryPeakAfter = memory_get_peak_usage();
 			$job = $jobList->getNext();
 			if ($job != null) {
 				$logger->debug('WebCron call has selected job with ID ' . strval($job->getId()), ['app' => 'cron']);
-				$job->start($jobList);
+				/** Calling execute until it is removed, then will switch to start */
+				$job->execute($jobList);
 				$jobList->setLastJob($job);
 			}
 			OC_JSON::success();