Load fewer classes when AndroidKeyStore provider is installed.

This avoids loading all AndroidKeyStore crypto SPI classes when the
AndroidKeyStore provider is instantiated and installed. This provider
is installed early on during the initialization of each app. Most apps
don't need these classes loaded.

Bug: 18088752
Change-Id: Ib43c9dd6a7d434b128916e0f9c8652ba61df0d47