Address sonar issues in ONAP-logging

Addressed the following sonar issues in ONAP-logging:
- use Map instead of ConcurrentHashMap
- remove unusued fields
- use Map.computeIfAbsent() instead of get()/put() pair
- readObject is unsafe
- use try-with-resources
- junit should assert something

Also removed some unused imports.

Issue-ID: POLICY-2305
Signed-off-by: Jim Hahn <jrh3@att.com>
Change-Id: I3480a55da4d0e771f8083c97770a6c9707d871f7
Signed-off-by: Jim Hahn <jrh3@att.com>
diff --git a/common-logging/pom.xml b/common-logging/pom.xml
index 1fef17a..a87d31a 100644
--- a/common-logging/pom.xml
+++ b/common-logging/pom.xml
@@ -67,6 +67,11 @@
             <artifactId>commons-lang3</artifactId>
         </dependency>
         <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
             <groupId>org.powermock</groupId>
             <artifactId>powermock-api-mockito2</artifactId>
             <scope>test</scope>