Clean up more schema before JDBC tests

https://build.spring.io/browse/INT-FATS5IC-843/

**Cherry-pick to 5.1.x & .5.0.x**

Author: artembilan

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/store/JdbcMessageStoreTests-context.xml

@@ -6,6 +6,7 @@
 			http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd">
 
 	<jdbc:embedded-database id="dataSource" type="H2">
+		<jdbc:script location="org/springframework/integration/jdbc/schema-drop-h2.sql"/>
 		<jdbc:script location="org/springframework/integration/jdbc/schema-h2.sql" />
 	</jdbc:embedded-database>
 

spring-integration-jdbc/src/test/java/org/springframework/integration/jdbc/store/channel/DataSource-derby-context.xml

@@ -17,6 +17,7 @@
 		/> </bean> -->
 
 	<jdbc:initialize-database data-source="dataSource">
+		<jdbc:script location="classpath:org/springframework/integration/jdbc/schema-drop-derby.sql" />
 		<jdbc:script location="classpath:org/springframework/integration/jdbc/schema-derby.sql" />
 	</jdbc:initialize-database>