Improve logging in GetPolicies initialization

[lucasmoten]

This likely also applies for other services.

During the initialization of the GetPolicies processor, if the SSL Context Service property is defined in setUpClient, then the setSslSocketFactory function is called to prepare the key manager and trust manager from the provided configuration. If these fail, they can throw exceptions: IOException, KeyStoreException, CertificateException, NoSuchAlgorithmException, UnrecoverableKeyException, KeyManagementException

In the case of an incorrect password or other misconfiguration resulting in UnrecoverableKeyException, it is not clear in the error being passed back which property is configured wrong. A typical error appears as follows in the NiFi Canvas bulletin board error

Failed to properly initialize Processor. If still scheduled to run, NiFi will attempt to initialie and run the Processor again after the 'Administrative Yield Duration' has elapsed. Failure is due to java.security.UnrecoverableKeyException: Cannot recover key: java.security.UnrecoverableKeyException: Cannot recover key

It would be useful if the processor logged whether this was thrown from handling the key store or the trust store.