Don’t reuse platform classloader when ScalaInstallation matches its version.

Remove the optimization that reused the platform class loader when the desired
Scala version matched the one installed in Eclipse. This proved to break due
to OSGi restrictions and the implementation of DelegatingReporter in the
compiler-interface.jar

See #1002175 for details
Merge pull request #733 from dragos/issue/fix-nightly-build

Don’t reuse platform classloader when ScalaInstallation matches its version