MULE-7050: MuleApplicationClassLoader loadClass() method not synchronize...

...d

_Adding synchronizing FineGrainedControlClassLoader#loadClass(String,boolean)
_Removing  MuleApplicationClassLoader#loadClass(String, boolean) override
_Adding test to verify the fix
_Renaming FineGrainedControlClassLoaderTest to FineGrainedControlClassLoaderTestCase