Log4j build fix on 0.9 branch

Spark should include log4j by default. Downstream packagers can exclude log4j
if they want to use another logging backend.

Author: pwendell

core/pom.xml

@@ -189,7 +189,6 @@
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-log4j12</artifactId>
-            <scope>test</scope>
         </dependency>
     </dependencies>
     <build>