Fix injection of AuditWriterToAsyncAppender

Add missing injection annotation to allow the audit writer
to be instantiated.

Change-Id: Ic8d2428736566fd6da5ae0864cb5f59726345726

src/main/java/com/googlesource/gerrit/plugins/auditsl4j/AuditWriterToAsyncAppender.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/auditsl4j/AuditWriterToAsyncAppender.java b/src/main/java/com/googlesource/gerrit/plugins/auditsl4j/AuditWriterToAsyncAppender.java
index 194af59..8ae8d68 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/auditsl4j/AuditWriterToAsyncAppender.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/auditsl4j/AuditWriterToAsyncAppender.java
@@ -16,6 +16,7 @@
 
 import com.google.gerrit.server.util.SystemLog;
 import com.google.gerrit.server.util.time.TimeUtil;
+import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import org.apache.log4j.AsyncAppender;
 import org.apache.log4j.Level;
@@ -28,6 +29,7 @@
   private final Logger log = Logger.getLogger(LoggerAudit.AUDIT_LOGGER_NAME);
   private final AsyncAppender appender;
 
+  @Inject
   public AuditWriterToAsyncAppender(AuditConfig config, SystemLog systemLog) {
     String logName = config.getLogName().get();
     appender = systemLog.createAsyncAppender(logName, new PatternLayout());