GUACAMOLE-234: Exclude slf4j from Apache Directory dependency.

extensions/guacamole-auth-ldap/pom.xml

@@ -146,6 +146,12 @@
             <groupId>org.apache.directory.api</groupId>
             <artifactId>api-all</artifactId>
             <version>2.0.0.AM2</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.slf4j</groupId>
+                    <artifactId>slf4j-api</artifactId>
+                </exclusion>
+            </exclusions>
         </dependency>
 
         <!-- Guice -->