Extract concurrent ce worker test to its own class test

Extract concurrent ce worker test to its own class test

When tests are in the same class, a Deadlock is generated on MySQL :
### Error updating database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
### The error may involve org.sonar.db.ce.CeActivityMapper.insert-Inline
### The error occurred while setting parameters
### SQL: insert into ce_activity (       uuid,       component_uuid,       analysis_uuid,       status,       task_type,       is_last,       is_last_key,       submitter_login,       submitted_at,       worker_uuid,       execution_count,       started_at,       executed_at,       created_at,       updated_at,       execution_time_ms,       error_message,       error_stacktrace,       error_type     )     values (       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?,       ?     )
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:200)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.insert(DefaultSqlSession.java:185)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:57)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
	at com.sun.proxy.$Proxy22.insert(Unknown Source)
	at org.sonar.db.ce.CeActivityDao.insert(CeActivityDao.java:55)
	at org.sonar.ce.queue.CeQueueImpl.remove(CeQueueImpl.java:156)
	at org.sonar.ce.queue.InternalCeQueueImpl.remove(InternalCeQueueImpl.java:110)
	at org.sonar.ce.taskprocessor.CeWorkerImpl.finalizeTask(CeWorkerImpl.java:165)
	at org.sonar.ce.taskprocessor.CeWorkerImpl.executeTask(CeWorkerImpl.java:148)
	at org.sonar.ce.taskprocessor.CeWorkerImpl.findAndProcessTask(CeWorkerImpl.java:97)
	at org.sonar.ce.taskprocessor.CeWorkerImpl.withCustomizedThreadName(CeWorkerImpl.java:81)
	at org.sonar.ce.taskprocessor.CeWorkerImpl.call(CeWorkerImpl.java:73)
	at org.sonar.ce.taskprocessor.CeWorkerImpl.call(CeWorkerImpl.java:43)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)