Add possibility to run Infinispan-server testsuite also with 1.6xx JDKs

Currently, there is a restriction in Infinispan-server set by maven-enforcer-plugin as

<requireJavaVersion>
<version>[1.7,)</version>
</requireJavaVersion>

This prevents us from comfortable running Infinispan-server testsuite with JDKs version 1.6 etc.

As this restriction is required, it's needed to implement new profile for running tests with JDKs 1.6.

See jdk6testsuite profile here, in Infinispan parent/pom.xml, which solves this already for Infinispan: https://github.com/infinispan/infinispan/blob/master/parent/pom.xml