BZ-1103970 - UnsupportedOperationException when TaskService.getTasksAssignedAsPotentialOwner (old test deleted)

(cherry picked from commit 3d58375fd97913a214bb90fa0bf04c0d14571180)
kie-remote-client: more error handling (HTML error messages from server)

(cherry picked from commit 53038581384612c00be7cea4bdff8569dc32ed17)