Classloading for Custom Authorization Extension Prematurely Deletes Classpath in Standalone

In CDAP [StandaloneMain|https://github.com/cdapio/cdap/blob/d69fc4b0eb0691156e515343e0fa87e72e409471/cdap-standalone/src/main/java/io/cdap/cdap/StandaloneMain.java], the AuthorizerInstantiator unpacks the custom authorization extension JAR file into a folder in `data/tmp`. However, the AuthorizerInstantiator is actually created in the constructor for StandaloneMain, and then cleanupTempDir() is called in startup(). This causes the unpacked JAR files to be deleted immediately after instantiation.

ClassLoaders generally perform lazy loading, which means that if an authorization extension attempts to load a class after this runtime classpath is deleted, it will throw a ClassNotFoundException.