Change integration tests from parallel to single

This is an attempt to make the Travis CI integration tests more reliable,
and changes from parallel to single forking mode.
This is a temporary measure until cucumber-jvm-parallel-plugin (which is no
longer supported) is ripped out (see #1240)

Signed-off-by: Andrew DeMaria <lostonamountain@gmail.com>

integration-test/pom.xml

@@ -196,8 +196,8 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
                 <configuration>
-                    <parallel>all</parallel>
+                    <forkCount>1</forkCount>
-                    <threadCount>2</threadCount>
+                    <reuseForks>false</reuseForks>
                     <includes>
                         <include>**/Parallel*IT.class</include>
                     </includes>