Improve CsrfBeanDefinitionParser xml parsing

1. CsrfBeanDefinitionParser registers requestDataValueProcessor
if not already registered
2. Created Tests in CsrfBeanDefinitionParserTests

Fixes: gh-6423

config/src/test/resources/org/springframework/security/config/http/CsrfBeanDefinitionParserTests-RegisterDataValueProcessorOnyIfNotRegistered.xml

@@ -0,0 +1,31 @@
+<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	   xmlns:context="http://www.springframework.org/schema/context"
+	   xmlns:tx="http://www.springframework.org/schema/tx" xmlns:util="http://www.springframework.org/schema/util"
+	   xmlns:security="http://www.springframework.org/schema/security"
+	   xsi:schemaLocation="
+http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
+http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
+http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
+http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd
+http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security.xsd
+">
+
+	<security:http pattern="/foo/**">
+		<security:intercept-url pattern="/**" access="hasRole('FOO')" />
+		<security:http-basic/>
+	</security:http>
+
+	<security:http pattern="/bar/**">
+		<security:intercept-url pattern="/**" access="hasRole('BAR')" />
+		<security:http-basic/>
+	</security:http>
+
+	<security:authentication-manager >
+		<security:authentication-provider>
+			<security:user-service>
+				<security:user name="gnu" password="{noop}gnat" authorities="ROLE_FOO" />
+			</security:user-service>
+		</security:authentication-provider>
+	</security:authentication-manager>
+
+</beans>