Revise database initialization.

Initializing the Keystore 2.0 database will now open the files
persistent.sql and perboot.sql. Tables are created, if they don't
exist, once per service startup instead of on every connection
instantiation. In the test situation we make use of the module
private visibility to create in-memory test databases or attaching
to a set of temporary files.

Test: keystore2_test
Bug: 159370859
Change-Id: I88594dabc72483779d980e81dbc05f2b7a687437
1 file changed