Keystore 2.0: No longer install the legacy provider.

The legacy provider is obsolete now that all calling code has
been fixed.

Bug: 183100147
Bug: 183093711
Bug: 171305684
Test: N/A
Merged-In: I0d71d3c9cdd586a508827eb26120c872cb8643ea
Change-Id: I0d71d3c9cdd586a508827eb26120c872cb8643ea