Remove maven-failsafe-plugin in infinispan-server-runtime

infinispan-server-runtime uses both maven-surefire-plugin and maven-failsafe-plugin, which makes it confusing sometimes. E.g. when trying to run a single integration test with -Dit.test=SomeIT, the surefire tests still run.

maven-failsafe-plugin 3.0.0 is supposed to replace -DskipTests with -DskipITs, so both -DskipTests -Dit.test=SomeIT and -DskipITs -Dtest=SomeTest will work. They haven't yet removed it in version 3.0.0-M4, but if we decide to keep both plugins after all, we can emulate the new behaviour with

               <skipTests>${skipITs}</skipTests>