jackson: use 2.8.6 - avoid bugs in 2.8.8

People are having issues with jackson 2.8.8 as required by helios-test
due to this issue: FasterXML/jackson-databind#1756

Author: Daniel Norberg

pom.xml

@@ -157,32 +157,32 @@
             <dependency>
                 <groupId>com.fasterxml.jackson.dataformat</groupId>
                 <artifactId>jackson-dataformat-yaml</artifactId>
-                <version>2.8.8</version>
+                <version>2.8.6</version>
             </dependency>
             <dependency>
                 <groupId>com.fasterxml.jackson.datatype</groupId>
                 <artifactId>jackson-datatype-guava</artifactId>
-                <version>2.8.8</version>
+                <version>2.8.6</version>
             </dependency>
             <dependency>
                 <groupId>com.fasterxml.jackson.core</groupId>
                 <artifactId>jackson-core</artifactId>
-                <version>2.8.8</version>
+                <version>2.8.6</version>
             </dependency>
             <dependency>
                 <groupId>com.fasterxml.jackson.core</groupId>
                 <artifactId>jackson-annotations</artifactId>
-                <version>2.8.8</version>
+                <version>2.8.6</version>
             </dependency>
             <dependency>
                 <groupId>com.fasterxml.jackson.core</groupId>
                 <artifactId>jackson-databind</artifactId>
-                <version>2.8.8</version>
+                <version>2.8.6</version>
             </dependency>
             <dependency>
                 <groupId>com.fasterxml.jackson.jaxrs</groupId>
                 <artifactId>jackson-jaxrs-json-provider</artifactId>
-                <version>2.8.8</version>
+                <version>2.8.6</version>
             </dependency>
             <dependency>
                 <groupId>joda-time</groupId>