Make TomcatEmbeddedWebappClassLoader parallel capable

[wilkinsona]

With reference to DATAMONGO-1792, the synchronization of TomcatEmbeddedWebappClassLoader.loadClass(String, boolean) is inefficient. Rather than making the method itself synchronized it should synchronize on the response from (getClassLoadingLock(className). We should also verify that the JVM considers the class loader to be parallel capable (its superclass is registered as such).

[wilkinsona]

There's no benefit to making the change proposed above. The super class, org.apache.catalina.loader.WebappClassLoader, is not parallel capable so TomcatEmbeddedWebappClassLoader cannot be parallel capable.

[wilkinsona]

As pointed out in DATAMONGO-1792, we could subclass ParallelWebAppClassLoader instead. That would be a breaking change, though, so it could only happen in 2.0.