BATCH-2248: Fixes for Ldif reader tests

Conflicts:
	spring-batch-core-tests/src/test/java/org/springframework/batch/core/test/ldif/LdifReaderTests.java
	spring-batch-core-tests/src/test/java/org/springframework/batch/core/test/ldif/MappingLdifReaderTests.java
	spring-batch-core-tests/src/test/resources/applicationContext-test1.xml
	spring-batch-core-tests/src/test/resources/applicationContext-test2.xml
Change prefetch on jms tests to 0 and add @DirtiesContext to tests

With the upgrade to ActiveMQ 5.9.0 as part of Spring IO, ActiveMQ's
prefetch behavior changed.  With each call to
JmsTemplate#receiveAndConvert, the template creates a new consumer.  In
these tests, the first call created a consumer which prefetched all the
test messages on the queue, leaving them unavailable for the second
consumer the JmsTemplate created.  By setting prefetch to 0, the
messages are now available for the subsequent
JmsTemplate#receiveAndConvert calls.  This addresses BATCH-2248.

Conflicts:
	spring-batch-infrastructure-tests/src/test/java/org/springframework/batch/repeat/jms/SynchronousTests.java