Fix android IceSSL testing

[pepone]

This PR fixes Android SSL testing, see #3288

With Ice 3.7, we relied on delaying IceSSL plug-in initialization and then manually setting the key store or trust store from the test controller helper in the communicator-initialized hook.

With Ice 3.8, this approach doesn't work because IceSSL is no longer a plug-in. It’s now a built-in transport, and its configuration must either be specified using IceSSL properties (as before) or when the communicator is created (client side) or the object adapter is created (server side).

Using the new native SSL APIs would require reviewing all object adapter creation in the test suite to correctly set the SSL configuration. For the client side, communicators are already created with a helper method, which simplifies things.

To keep it simpler, I added a new resourceLoader member to InitializationData that allows loading certificates using a custom loader; in this case, we want to load them from Android resources.

If we don’t want to take this approach of adding a new resourceLoader, an alternative would be to set the existing classLoader and wrap it with a decorator that re-implements getResourceAsStream.

[externl]

Seems good to me!