Upgrade org.mockito:mockito-core to 3.0.0

Fixes gh-7145

[closes #7145]

Author: fhanik

gradle/dependency-management.gradle

@@ -180,7 +180,7 @@ dependencyManagement {
 		dependency 'org.jboss.logging:jboss-logging:3.3.1.Final'
 		dependency 'org.jboss.spec.javax.transaction:jboss-transaction-api_1.2_spec:1.0.1.Final'
 		dependency 'org.jboss:jandex:2.0.3.Final'
-		dependency 'org.mockito:mockito-core:2.27.0'
+		dependency 'org.mockito:mockito-core:3.0.0'
 		dependency 'org.objenesis:objenesis:2.6'
 		dependency 'org.openid4java:openid4java-nodeps:0.9.6'
 		dependency 'org.ow2.asm:asm:6.2.1'