Prevent a task from starting if an inst with the same name is running.

resolves #81

Using LockRegistryLeaderInitiator to do leadership election.

When task is started and singleInstanceEnabled isset to true then we use leader election
to determine if a task needs to be started.

Error Event Name had to be updated

spring-cloud-task-integration-tests/pom.xml

@@ -84,6 +84,16 @@
 			<artifactId>h2</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.integration</groupId>
+			<artifactId>spring-integration-core</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.integration</groupId>
+			<artifactId>spring-integration-jdbc</artifactId>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 	<build>
 		<plugins>