fix logback jar security issue

Change-Id: I51e0fec8131db5f5283182c1fc70a4f5b023dbb1
Issue-ID: APPC-652
Signed-off-by: Taka Cho <tc012c@att.com>
diff --git a/appc-directed-graph/dg-loader/pom.xml b/appc-directed-graph/dg-loader/pom.xml
index 866f07c..9ad7c76 100644
--- a/appc-directed-graph/dg-loader/pom.xml
+++ b/appc-directed-graph/dg-loader/pom.xml
@@ -45,7 +45,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <java.version.source>1.8</java.version.source>
         <java.version.target>1.8</java.version.target>
-        <logback.version>1.1.1</logback.version>
+        <logback.version>1.2.3</logback.version>
         <common.collections.version>3.2.1</common.collections.version>
         <common.io.version>2.5</common.io.version>
         <jettison.version>1.3.7</jettison.version>