Upgrade Spotbugs to 3.1.1

Change-Id: Ie43c74acabd9520dde5d8577f040e6575bd3ebbc
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

pom.xml

@@ -210,7 +210,7 @@
     <maven-javadoc-plugin-version>3.0.0</maven-javadoc-plugin-version>
     <tycho-extras-version>1.0.0</tycho-extras-version>
     <gson-version>2.2.4</gson-version>
-    <spotbugs-maven-plugin-version>3.1.0</spotbugs-maven-plugin-version>
+    <spotbugs-maven-plugin-version>3.1.1</spotbugs-maven-plugin-version>
     <maven-surefire-report-plugin-version>2.20.1</maven-surefire-report-plugin-version>
 
     <!-- Properties to enable jacoco code coverage analysis -->