failIfNoTests=false should not be required when using -Dtest=MyTestClass in multi-module reactor builds

Configure a trivial multi-module build with two tests (TestA, TestB) and two modules, one test in each module.

a multi-module aggregate build will succeed with

'mvn test'

but fail with

'mvn test -Dtest=TestA'

This happens with 2.10, but does not with 2.6 for http://avro.apache.org/ (https://issues.apache.org/jira/browse/AVRO-935)

This is related to bug
http://jira.codehaus.org/browse/SUREFIRE-464

-Dtest=Foo should not require that every module have a matching Foo, only one needs match. Or to simplify things, don't automatically switch from failIfNoTests=false to failIfNoTests=true when -Dtest= is set at all.

Users who are running one test by hand don't need this behavior (they will notice if the test they are trying to run doesn't run) and automated tools/scripts that use this parameter that want it to fail should set -DfailIfNoTests=true.