[ONOS-3737] Bump up checkstyle version from 2.16 to 2.17 with some compilation fixes

Change-Id: I3ade52ff15b3114f5748ab3151c02c8c74af38f0
diff --git a/pom.xml b/pom.xml
index 003a9d4..13a3ef1 100644
--- a/pom.xml
+++ b/pom.xml
@@ -698,7 +698,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-checkstyle-plugin</artifactId>
-                <version>2.16</version>
+                <version>2.17</version>
                 <dependencies>
                     <dependency>
                         <groupId>org.onosproject</groupId>