Fix last step execution retrieval in MongoStepExecutionDao

Resolves spring-projects-experimental/spring-batch-experimental#3

Author: fmbenhassine

spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/MongoStepExecutionDao.java

@@ -111,6 +111,7 @@ public StepExecution getLastStepExecution(JobInstance jobInstance, String stepNa
 		// first one
 		Optional<org.springframework.batch.core.repository.persistence.StepExecution> lastStepExecution = stepExecutions
 			.stream()
+			.filter(stepExecution -> stepExecution.getName().equals(stepName))
 			.min(Comparator
 				.comparing(org.springframework.batch.core.repository.persistence.StepExecution::getCreateTime)
 				.thenComparing(org.springframework.batch.core.repository.persistence.StepExecution::getId));